EP0393117A4

EP0393117A4 - Protocol for network having a plurality of intelligent cells

Info

Publication number: EP0393117A4
Application number: EP19890900454
Authority: EP
Inventors: Wendell B. Sander; William B. Twitty
Original assignee: Echelon Systems Corp
Current assignee: Echelon Systems Corp
Priority date: 1987-11-10
Filing date: 1989-05-24
Publication date: 1991-08-28
Anticipated expiration: 2008-11-01
Also published as: GB9007629D0; JPH03505642A; GB2244830B; EP0393117B1; AU634079B2; DE3890947C2; CA1317651C; WO1989004517A1; JPH0578054B2; SG86292G; GB2244830A; EP0393117A1; AU8153791A

Abstract

A network for providing sensing, communications and control has a plurality of intelligent programmable cells (27, 28). Each cell has an integrated circuit with a processor (100). A network is distinguished from another network by system identification numbers (IDs). Groups of cells within each network are formed to perform particular functions and are identified by group IDs. Communications occur within the network through use of the system, group and cell IDs. Some cells are assigned the task of sensing, for example, the condition of a switch, and other cells the task of controlling, such as controlling a light. The preferred embodiment of the cell includes a multiprocessor and multiple I/O subsections where any of the processor can communicate with any of the I/O subsections. This permits the continual execution of a program without potential interruptions caused by interfacing with the I/O section. The I/O section includes programmable A-to-D and programmable D-to-A converter.

Description

PROTOCOL FOR NETWORK HAVING A PLURALITY OF INTELLIGENT CELLS

BACKGROUND OF THE INVENTION 1 . Field of the Invention

The invention relates to the field of networks with distributed intelligence, configuration and control and intelligent cells used in networks, primarily where the networks are used for sensing, communicating and controlling.

2. Prior Art.

There are many commercially available products which provide sensing, control and communications in a network environment. These products range from very expensive, elaborate systems, to simple systems having little intelligence. As will be seen, the present invention is directed towards providing a system having a relatively large amount of intelligence and computational power but at a low cost. One commercially available system "X-1 0" provides control, by way of example, between a light switch and a light. When the light switch is operated, a code pattern is transmitted over the power lines to a receiver at the light. The code pattern is transmitted twice, once in its true form and once in its complementary form. When the code is received by the receiver, it is interpreted, and thereby used to control the light. Mechanical addressing means are employed, to allow the transmitter at the switch to communicate with the specific desired receiver at the light.

As will be seen, the present invention provides substantially more capability and flexibility than current systems.

Applicant will submit prior art references on X-10 and other known prior art systems.

SUMMARY OF THE INVENTION

A network for providing sensing, communications and control is described. A plurality of intelligent cells each of which comprises an integrated circuit having a processor and input/output section are coupled to the network. Each of the programmable cells receives when manufactured a unique identification number (48 bits) which remains permanently within the cell. The cells can be coupled to different media such as power lines, twisted pair, radio frequency, infrared ultrasonic, optical coaxial, etc., to form a network.

Networks are distinguished from one another by system identification numbers (IDs). Groups of cells within each network are formed to perform particular functions and are identified by group IDs. Communications occur within the network through use of the system, group and cell IDs. Some cells (announcers) are assigned the task of sensing, for example, the condition of a switch, and others (listeners) the task of controlling, such as controlling a light. Cells can perform multiple tasks and be members of multiple groups, and, for example, can act as a repeater for one group and a listener in a another group. When manufactured, the cells are identical except for the cell ID; they are programmed to perform specific tasks for a particular group or groups.

The preferred embodiment of the cell includes a multiprocessor and multiple I/O subsections where any of the processors can communicate with any of the I/O subsections. This permits the continual execution of a program without potential interruptions caused by interfacing with the I/O section. The I/O section includes programmable A-to-D and programmable D-to-A converters as well as other circuits for other modes of operation.

The network protocol provides great flexibility, and for instance, allows groups to be formed and/or changed after the cells are in place. As will be seen, the intelligence for the network is distributed among the cells. In general, the network is lightly loaded, although provisions are made for contention and other conditions which may arise. The communication between the cells in general is optimized for carrying out the functions assigned to groups, rather than for transmission of data unrelated to the control function of the network. For this reason, normally the packets carrying messages are relatively short compared to Ethernet, Arpa, AppleTalk, X-25 and many other broadband and data communication systems. Other aspects of the invented network and cell will be apparent from the detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a block diagram illustrating typical application for the present invention.

Figure 2 is a diagram used to illustrate the grouping of cells.

Figure 3 is another block diagram similar to Figure 2 used to illustrate the grouping of cells.

Figure 4 is a diagram used to describe subchannels.

Figure 5 is a diagram illustrating a plurality of cells; this diagram is used to describe cell group formation employing the present invention.

Figure 6 is a chart illustrating the packet format used with the present invention.

Figure 7 is a chart illustrating the designation list portion of the packet format of Figure 6.

Figure 8 illustrates a series of steps used in forming a group of cell with the present invention.

Figure 9 is a chart illustrating the code assignments for the three-of-six encoding used with the present invention. Figure 10 is a block diagram of the communication and control cell. Figure 11 is a block diagram of a portion of the instruction decoding logic used within the processor of the cell of Figure 10

Figure 12 is a detailed block diagram of the process of Figure 10.

Figure 13 is a timing diagram for the processor of Figure 1 0; this diagram also shows latches and registers used to provide the pipelining employed by the cell.

Figure 14 is a block diagram illustrating the presently preferred embodiment of the three-of-six encoder.

Figure 1 5 is a block diagram showing the presently preferred embodiment of the three-of-six decoder.

Figure 1 6 is a block diagram showing the presently preferred embodiment of the three-of-six code verifier. Figure 1 7 is an electrical schematic of the buffer section of one of the I/O sections.

Figure 1 8 is an electrical schematic of the counting and timing functions for an I/O subsection.

Figure 1 9 is an electrical schematic of the control and state machine for an I/O section.

Figure 20 is an electrical schematic for the sample and hold means associated with the I/O subsections. Figure 21 illustrates the network formed within an I/O subsection to do digital-to-analog conversion.

Figure 22 illustrates the network formed within an I/O section for analog-to-digital conversion. Figure 23 is an electrical schematic showing the communications portion of an I/O subsection.

Figure 24 is a state diagram used for the I/O subsections and for transmission contentions.

Figure 25 is a state diagram for the link level ARQ. Figure 26 is a state diagram for primary station connections.

Figure 27 is a state diagram for secondary station connections.

Figure 28 is a block diagram for a grouping device. Figure 29 is a diagram showing the form in which the system ID is encoded for transmission by the packet and encoded within a cell.

Figure 30 is a diagram used to describe the operation of the input/output section and semaphore register.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

An apparatus and method for providing a communications, sensing and control in a network is described. Where the network contains a plurality of intelligent cells, the cells in general are programmable single chip remote control, sensing and communication devices that, when interconnected (via various media) with other cells, have distributed sensing, communication, control and network configuration intelligence, configuration and control. The system comprises a network of cells organized in a hierarchy based on communications needs. Cells are organized into working "groups" independent of the network hierarchy. Groups of cells generally are used to perform a group function. This function is carried out by the assignment of tasks to cells within the groups. Cells communicate, control and sense information. In general, each cell has a unique identification number and perform information processing tasks such as: bidirectional communications protocol, input/output, packet processing and analog and digital sensing and control. In general, the system comprised of the cells has the characteristic of storing network configuring information that is distributed throughout the system; and communicates automatically routed messages among cells. Each system also has a unique identification (ID) which in the presently preferred embodiment is 48 bits. Moreover, it contains versatile programmable input/output I/O circuits with digital versatile programming to configure cells to specific sensing, communication, control and I/O, analog I/O, communication I/O and communications bit rate sensing. In the following description, numerous specific details are set forth such as specific frequencies, etc., in order to provide a thorough understanding of the present invention. It will be obvious, however, to one skilled in the art that these details are not required to practice the invention. In other instances, well- known circuits, methods and the like are not set forth in detail in order not to unnecessarily obscure the present invention. I . OVERVIEW OF AN APPLICATION OF THE PRESENT

INVENTION

Before describing the present invention in detail, an understanding of a typical application will aid in appreciation of the details to follow. In Figure 1 , a simple, typical application is shown based on the use of the present invention in a home. In Figure 1, the switch 22 is used through the present invention to control the light 23.

The arrangement 20 comprises a cell 27 which is connected to the switch 22. The cell is also connected to a transceiver 29 which couples data onto the lines 24 and 25. Power for the transceiver and cell are provided from the power supply 30 which receives power from the lines 24 and 25. For this example, the lines 24 and 25 are ordinary household wiring (e.g., 1 1 0VAC) and the power supply 30, a five volt DC supply. The cell 27 is preferably an integrated circuit which is described in more detail beginning with Figure 10. The transceiver 29 may be any one of many well-known devices for receiving and transmitting digital data and as presently contemplated does not perform any processing on transmitted data. The entire arrangement 20 may be small enough to fit within an ordinary wallmounted electrical box which normally contains an electrical switch.

The arrangement 21 again may be small enough to fit within a typical electrical outlet box and includes a power supply 31 and transceiver 33 which may be identical in construction to the power supply 30 and transceiver 29, respectively. This cell 28 is coupled to the transceiver 30 and power supply 29 as well as the solenoid operated power switch 32. Cell 28 may be identical to cell 27 except for programming and an identification number which shall be discussed later. An output from the cell 28 controls the solenoid 32 to operate a power switch which in turn connects the light 23 to the power lines 34 and 35. The cell 28, as will be seen, can provide a digital or analog output, which can control a rheostat (not shown) or the like, thus enabling the dimming of the light 23.

The break 26 in the power lines 24 and 25 is used to indicate that the power lines 24 and 25 may not necessarily be on the same circuit as power lines 34 or 35. As will be seen, the transceiver 29 may not necessarily communicate directly with transceiver 33, but rather communication between the transceivers may require linkage through another cell and transceiver which repeats packets sent between the arrangements 20 and 21 . In Figure 1, the transceivers 29 and 33 communicate over power lines. The transceivers may communicate with one another in numerous different ways over countless media and at any baud rate. They may, for example, each transmit and receive radio frequency or microwave frequency signals through antennas. The transceivers could be connected to a communications lines, such as an ordinary twisted pair or fiberoptic cable and thus communicate with one another independent of the power lines. Other known communications medium may be employed between the transceivers such as infrared or ultrasonic transmissions. Typical transmission rates are 10K bits per second (KBPS) for power lines. Much higher transmission rates are possible for radio frequency, infrared, twisted pairs, fiberoptic links and other media.

Cell 27 senses the opening or closing of the switch 22, then prepares a packet which includes a message initiating the state of the switch 22; the packet is communicated to the cell 28 through transceiver 29, lines 24 and 25, lines 34 and 35, and transceiver 33. The cell 28 acknowledges the message by returning a packet to the cell 27 and also acts upon the message it received by turning on or off the light 23 by operating the solenoid controlled power switch 32.

Each cell has a unique 48 bit identification number (ID number), sometimes referred to as the cell address. In the currently preferred embodiment, each cell as part of the manufacturing process, receives this permanent and unique ID number. (It cannot be changed following manufacturing.) As will be appreciated, with approximately 2⁴⁸ possible ID numbers, each cell will have a unique ID number no matter how large a network becomes for practical purposes, or no matter how many networks are interconnected. The grouping device then accesses the individual cell IDs and assigns a system ID to each cell. In addition, the grouping device configures the cells into groups to perform group related functions.

For the illustration of Figure 1, cell 27 is designated as "A" to indicate that its primary function is to "announce" that is, transmit the state of switch 22 on the network communications lines 24 and 25, and 34 and 35. On the other hand, cell 28 is designated with the letter "L" since its primary function in Figure 1 is to "listen" to the network and in particular to listen to messages from cell 27. In subsequent figures, the "A" and "L" designations are used, particularly in connection with a group formation of multiple cells to indicate an announcer arrangement, such as arrangement 20 and a listener arrangement, such as arrangement 21. For purposes of discussion the cells themselves are sometimes referred to as transmitting or receiving data without reference to transceivers. (In some cases, the transceivers may be a simple passive network or simple wires, which couple the input/output of a cell onto a line. As will be seen the I/O section of the cells can provide output signals that can drive a twisted pair or the like. Thus the cells themselves can function as a transceiver for some media.)

The cells 27 and 28 as will be described subsequently are processors having multiprocessor attributes. They may be programmed prior to or after installing to perform their required function, such as an announcer or listener and for grouping combinations.

NETWORK ORGANIZATION AND DEFINITIONS A. Definitions Cell: A cell is an intelligent, programmable element or elements providing remote control, sensing and/or communications, that when interconnected with other like elements form a communications, control and sensing network or system with distributed intelligence. Announcer: An announcer is a source of group messages.

Listener: A listener is a sink of group messages. (An announcer in some cases may request state information from a listener.)

Reoeater: A repeater is a cell which in addition to other functions reads packets from a medium and rebroadcasts them. Group: A set of cells which work together for a common function (for example, a switch controlling a set of lights) is referred to as a "group".

In Figure 2, the group 37 has an announcer 37a, listeners 37b, and 37c, and a listener 40. A group 38 includes an announcer 38a, listeners 38b and 38c and the listener 40. Figure 2 illustrates that a single cell (cell 40) may be a listener in two groups. If announcer 37a has a light switch function, it can control lights through cells 37b, 37c and 40. Similarly, a switch associated with announcer 38a can control lights through cells 37c, 37b, and 40. In Figure 3, a group 42 includes announcers 44, 45 and listeners 46 and 47. The group 43 shares cell 44 with group 42; however, cell 44 is a listener for group 43. The group 41 shares cell 47 with group 42; cell 47 is an announcer for group 41 and for example, can announce to the listener 48 of group 41. Cell 47 also operates as a listener for group 42. A single cell as shown may be an announcer for one group and a listener for another group (cells are programmed to perform these functions, as will be discussed). However, as presently contemplated, a single cell cannot announce for more than one group. (In the currently preferred embodiment each cell has three input/output pairs of lines and a select line. Each pair shares a common set of resources. The lines may be used independently for some functions where the required shared resources do not conflict. In other functions, the lines are used as pairs. In this example, a pair of leads from cell 27 are coupled to a light switch and another pair are used for communications from the announcer, cell 27.) Subchannel: In Figure 4, a first plurality of cells are shown communicating through a common medium such as a twisted pair 50 (cells are shown as "C", announcers as "A" and listeners as "L"). This (e.g., twisted pair 50) is defined as a subchannel, that is, a set of cells all of which communicate directly with one another over the same medium. A broadcast by any member of the subchannel, such as the cell 49, will be heard by all members of that subchannel over the twisted pair 50.

Channel: A channel comprises two or more subchannels where all the cells communicate using the same medium. In

Figure 4, another plurality of cells are shown coupled to twisted pair 52 forming another subchannel. Assume cells 56 and 57 communicate between one another through a twisted pair 72. They form yet another subchannel. The cells associated with the twisted pairs 50, 52 and 72 comprise a single channel. It is possible that the twisted pairs 50, 52 and 72 are one continuous twisted pair with one subchannel 50 so far apart from the second subchannel 52 that the only communications between subchannels is over the portion of the twisted pair 72 running between cells 56 and 57. In this case the cells 56 and 57 are assigned to be

"repeaters" in addition to whatever other function they may serve (e.g., announcer or listener). A group 55 is illustrated in Figure 4 which comprises an announcer and listener in the two different subchannels. Another group 75 is illustrated comprising an announcer on one subchannel 51 and subchannel 52, where the subchannels are not part of the same channels since they use different media.

Gateway: A gateway reads packets from two different media and rebroadcasts them. A cell may be a gateway. Communications between channels is through gateway 54. In Figure 4, an additional subchannel which includes the cell 58 is coupled to another medium 51, for example, a common power line. The cell 58 is shown connected to channel gateway 54 which in turn communicates with the twisted pair 52. The gateway 54 does not necessarily perform either an announcer or listener function, but rather for the illustrated embodiment, performs only a channel gateway function by providing communication between two different media.

Subnetwork: A subnetwork comprises all the ceils having the same system identification (system ID). For example, all the cells in a single family home may have the same system ID. Therefore, the channels of Figure 4 may be part of the same subnetwork in that they share the same system ID. Full Network: A full network may comprise a plurality of subnetworks each of which has a different system ID; a communications processor is used for exchanging packets between subnetworks. The communications processor translates packets changing their system ID, addressing and other information. Two factory buildings may each have their own system ID, but control between the two is used by changing system IDs. (The word "network" is used in this application in its more general sense and therefore refers to other than a "full network" as defined in this paragraph.) Other terms used later are: Probe Packet: A packet routed by flooding which accumulates routing information as it travels through the network. Grouping Device: A device that controls determination of routes among cells, assigns cells to groups, and assigns function to group members.

Contention: The state which exists when two or more cells attempt to transmit a broadcast on the same subchannel at the same time and their signals interfere. B. GROUP FORMATION

1. Cells Assigned to a group by a postinstallation grouping device.

Assume that the plurality of cells shown in Figure 5 are all connected to communicate over the power lines in a home and are part of the same channel. Further assume that one cell, announcer 60, is to be grouped with the listener 65. The lines between the cells such as line 59 is used to indicate which of the cells can communicate directly with one another, for instance, announcer 60 and cell 61 can communicate with one another. (Cells 61, 62, 63, 64 and 66 of course may be announcers or listeners in other groups, but for purposes of explanation are shown as "C" in Figure 5.) Since announcer 60 and cells 61, 62, and 63 all communicate with one another, they are on the same subchannel. Similarly, cells 62, 64, 65 and 66 are another subchannel. (There are other subchannels in Figure 5). Importantly, however, announcer 60 and listener 65 are in different subchannels of the channel of Figure 5 and there are numerous routes by which a message can be passed from announcer 60 to listener 65, for example, through cells 61 and 64 or through cells 62 and 64, etc.

Note that even though all the cells are on the same power system of a house, they may not communicate directly with one another. For instance, the announcer 60 may be on one circuit which is only coupled to the listener 65 through long lengths of wire running the length of a home and a low impedance bus bar of a circuit breaker panel. The high frequency communication messages may be sufficiently attenuated through this path to prevent direct communications between cells even though they are physically close to one another.

For the following description, it is assumed that each of the cells can broadcast without interfering with the broadcast of other cells. That is, messages do not interfere with one another. The case where some contention occurs is dealt with under the protocol section of this application. In one embodiment, the group of announcer 60 and listener 65 is formed by using the grouping device shown in Figure 28. Note that before this group is formed the announcer 60 and listener 65 are ordinary cells, not designated to be an announcer and listener. Each grouping device may be assigned a unique 48 bit system ID at time of manufacture (in the presently preferred embodiment a 48 bit number is used). In the presently preferred embodiment, a cell is included with each grouping device. The cell's ID becomes the system ID. This assures that each system has a unique system ID. By way of example, each home has its own "grouping" device and hence, its own system ID for the subnetworks used in the home. This system ID is used in cell packets for the subnetwork. In this example, the grouping device has available the cell IDs of cells 60 and 65. (Various methods of obtaining cell IDs will be described later.)

The grouping device is connected to cell 60 by communicating through one of its three pairs of input/output (I/O) lines of the cell (or the select pin) and the grouping device reads the 48 bit ID number of the cell 60. (Different methods of determining the cell's IDs are described in the next section.) The grouping device next generates a random bit binary number which in the presently preferred embodiment is 1 0 bits. This number functions as a group identification number (also referred to as the group address) for the group comprising the announcer 60 and listener 65. The grouping device checks this number against other group IDs which it has previously assigned to determine if the group ID has previously been used. If it has been already used it generates another number. (A single grouping device, for instance keeps track of all the group IDs assigned in a single home.) The grouping device programs the cell 60 designating it as an announcer. The grouping device may cause the announcer 60 to broadcast the group number in a special packet which asks all cells in the network to acknowledge the message if they have been designated as a member of this group. This is another way to verify that the group ID has not been used.

The grouping device now determines the ID number of the cell 65. This may be done by connecting the grouping device directly to the cell 65 even before the cell is installed or by other methods discussed in the next section. (A cell and a group can be assigned ASCII names, for example, "porchlight" (cell name) and "exterior lights" (group name). This is used to allow selection of cell IDs or group IDs by accessing the ASCII name.

Now the grouping device causes the announcer 60 to transmit a probe packet. The probe packet contains the ID of cell 65. The packet directs all cells receiving the packet to repeat it and directs cell 65 to acknowledge the packet. Each cell receiving the probe packet repeats it and adds to the repeated packet its own ID number. Each cell only repeats the packet once (the mechanism for preventing a probe packet from being repeated more than once is described later.)

The cell 65 receives the probe packet through numerous routes, including those which in the diagram appear to be most direct (via cell 62) and those which are longer, for example, via cells 61 and 64. It is assumed that the first probe packet to arrive at cell 65 took the most direct route and is therefore the preferred routing. (Assume that this is via cell 62.) Cell 65 receives a packet which indicates that the probe packet was transmitted by cell 60, repeated by cell 62 and intended for cell 65. The other probe packets received by cell 65 after this first packet are discarded by cell 65.

Cell 65 now transmits an acknowledgement back to announcer 60. This packet includes the routing of the probe packet (e.g., repeated by cell 62). The packet directs cell 62 to repeat the packet to confirm its receipt.

After announcer 60 receives the acknowledgement packet for cell 65 it determines that cell 62 must be a repeater. The grouping devices causes announcer 60 to send a repeater assignment packet which includes the unique ID number of cell 62, the group number and a message which informs cell 62 that it is assigned a repeater function for the group. This causes cell 62 to repeat all those packets for the group comprising announcer cell 60 and 65. Another message is sent from announcer 60 under control of the grouping device repeated by cell 62, designating cell 65 as a listener, causing it to act upon messages for the group (cell 65 becomes a group member.) The grouping device assigns members a member number whch is stored by member cells.

The group formation described above is shown in Figure 8 by steps or blocks 68 through 72. Block 68 illustrates the broadcasting of the probe packet (e.g., cell 60 transmits the initial probe packet to all cells). The packet includes the address of a destination cell. As the packet proceeds through the network, the packet and accumulates the ID numbers of those cells repeating the packet (block 69). Block 70 shows the acknowledgement (reply) to the probe packet from the destination cell (e.g., cell 65). This packet returns the ID numbers of the repeaters contained in the first received probe packet. Repeater assignment packets are sent out by the announcer causing each repeater to rebroadcast packets for the group; this is shown by block 71 . Finally, as shown by block 72, the destination cell such as cell 65 is designated as a listener. 2. Cells assigned to a group b y a preinstallation grouping device. There may be several types of preinstallation grouping devices, for example, see Figure 28 for a device which may be used. One type is a device that a manufacturer uses to preassign cells to groups. Another type of preinstallation grouping device is one that a retailer or other cell vendor may use to assign cells to groups before, installation.

A grouping device assigns a cell to a group and assigns the cell's function(s) for that group. The grouping device may also assign a system ID to the cell. The system ID assigned by a preinstallation grouping device is not necessarily a unique system ID. (Postinstallation grouping devices assign a unique system ID to each system.)

One method that may be used by preinstallation grouping devices to generate a system ID is to choose a system ID from a range of the 48 bit address and system ID numbers that have been set aside for use as preinstallation system IDs. Just as the cell IDs in the range 1 -1 023 have been set aside for use as group IDs and group addresses, the cell IDs in the range 1 024-2047 can be set aside for use as preinstallation system IDs. It is desirable that grouping devices and other network control devices be able to identify preinstallation system IDs as opposed to postinstallation system IDs. Since postinstallation sytem IDs are generated by copying a cell ID, cell IDs should not be assigned in the range set aside for preinstallation system IDs. Therefore, ID numbers in that range would not be assigned to cells as cell IDs. Cells may be sold in sets that have been preassigned to a group by the manufacturer. The type of preinstallation grouping device used by the manufacturer assigns cells to groups by writing the appropriate codes into the cells' nonvolatile memory. The user may install such a set of cells and it will operate without assignment by a postinstallation grouping device provided that the set of cells may communicate via a single subchannel.

A user may assign cells to a group at the time cells are purchased or at any other time before installation. Such cells, unlike the case previously discussed, are not assigned to groups by the manufacturer and are called unassigned cells. Unassigned cells all have the same system ID, a system ID number that has been set aside for use only by unassigned cells. The user assigns a set of cells to a group by using a preinstallation grouping device that may be different from the preinstallation grouping device used by a manufacturer.

Typically, such a grouping device will operate on one cell at a time. The operator commands the grouping device to generate a new group ID and system ID and then each cell is connected to the device in turn. The operator commands the grouping device to assign a cell to the group while the cell is connected to the grouping device. The grouping device assigns cells the same group ID and system ID until it is commanded by the operator to generate a new group ID and system ID.

The user may install such a set of cells and it will operate without use of a postinstallation grouping device provided that the set of cells can communicate via a single subchannel. 3. Unassigned Cells Grouping and Self-Assignment After Installation .

Unassigned cells may create a group and assign themselves to the group after installation in the following manner.

The first announcer cell that is stimulated via its sensor input (e.g., light switch) controls the group formation process. It chooses a system ID number at random from the range of system ID numbers that have been set aside for preinstallation grouping devices. It chooses a group ID number at random. It then broadcasts the group ID number in a packet that requests a reply from any cells that are members of that group. If the transmitting cell receives any such replies, it chooses another group ID at random. The cell continues this process of selecting a random group ID and testing to see if it is already in use until it finds a group ID that is unused in the system in which it is operating. An unassigned cell's default configuration information programmed at the factory identifies its function as either a listener or an announcer. If the unassigned cell is an announcer, it waits for its sensing input to be stimulated, and when it is stimulated, the cell transmits a packet addressed to a group. If an unassigned cell is a listener, it listens after power-up for a packet. The cell takes the group ID from the first packet it receives and assigns itself to that group. The cell then sends a reply to the announcer cell. This reply is not an acknowledgement only packet; it is a packet that identifies the cell as a listener in the group and the packet must be acknowledged by the announcer. This assures that all of the listener identification packets will arrive at the announcer even though there will be contention and collisions in the process. The cell that transmitted the group announcement builds a list of group members as each reply comes in. It then sends a packet to each listener assigning that listener a group member number. 4. Unassigned Cells Joining Preexisting Group After Installation. Unassigned cells may be added to existing systems and assigned to a group in a manner similar to the above method discussed in Section 3 above. A listener joins the system and a group by the same method as in Section 3 above. In the above example, the announcer waits to be stimulated via its sensor input. An unassigned announcer waits for its first sensor input stimulation or its first received packet. Of those two events, the event that occurs first determines the subsequent actions of the announcer cell. If the cell is stimulated first, it controls a group formation process just as in the above example. If the announcer cell receives a group packet first, it joins that group as an announcer. It then sends a packet to the group announcer requesting configuration information about the group (group size, number of announcers, etc.) and the assignment of a group member number.

C. METHODS OF IDENTIFYING A CELL FOR GROUPING In order for a grouping device to go through the steps necessary to form a group or add a cell to a group, it must know the IDs of the cells to be added to the group. The grouping device then uses those cell IDs to address commands to the cells during the grouping process. The methods that a user with a grouping device may use to obtain the cell IDs are listed below. Note that a grouping device or other control device's ability to communicate with a cell in the following example may be limited by security procedures if used. The security procedures, limitations on communications and levels of security are not critical to the present invention. The following example assumes that no security procedures are in place. In particular, it may be impossible for a grouping device to communicate with installed cells unless the grouping device has the system key (system ID and encryption keys.) 1 . Direct connection to the cell.

The grouping device may be connected to an I/O line of the cell package and then send a message to the cell requesting its ID. Physical connection can be used to find a cell's ID either before or after the cell is installed. Known means can be used (e.g., a fuse or a programmed disable command) to allow a user to disable this function in an installed cell to protect the security of the system. 2. Selection of the Cell Through Use of Special Pin

The user may use the grouping device or some other selection device to physically select the cell by stimulating a cell input pin that has been designated to serve the selection function. The grouping device communicates with the cell through the normal communications channels and sends a broadcast message requesting that all selected cells reply with their ID. Only one cell is selected so only that cell will reply to the request. Physical selection can be used to find a cell's ID either before or after the cell is installed. Again, a means can be provided to allow a user to disable this feature to protect the security of the system. 3. Query All Names of Previously Grouped Cells It is assumed in this example that ASCII "groups" and "cell" names have been previously assigned to the cells. For this method, the grouping device queries all of the cells in a system to report their group and cell names (ASCII name). The user scrolls through the list of group names by using the grouping device. The user selects the name of the group that is believed to contain the target cell. The grouping device displays the names of all of the cells that are in the group and their assigned tasks (announcer, listener, repeater). The user selects the name of the cell that is believed to be the target cell. If the selected cell is an announcer, the grouping device prompts the user to activate the announcer by stimulating its input. For example; if the cell is attached to a light switch, the user turns the switch on and off. The cell sends announcement packets to the group. The grouping device listens to the communications channel and discovers the group and member numbers or other codes of the activated announcer. If the selected cell is a listener cell, the grouping device sends packets to the cell (using the group and member numbers for addressing) commanding it to toggle its output. For example, if the cell controls a light, the light will flash on and off. This allows the user to verify that he has selected the correct cell.

The grouping device sends a packet (using group and member numbers for addressing) to the target cell with a command for the target cell to return its cell ID. The grouping device now knows the target ID and can proceed with the group assignment process.

Querying names is used to find a cell's ID before or after the cell is installed. 4. Stimulate Group.

This method is used in a network in which group and cell ASCII names have been assigned. The user commands the grouping device to wait for the next group announcement. Then the user stimulates the announcer in the group of interest. For example, if the announcer is a light switch, the user throws the switch. The grouping device hears the announcement packet and extracts the group ID from it.

The user may verify that this group ID is for the desired group by causing the grouping device to send packets to all of the group listeners commanding them to toggle their outputs. The user verifies that it is the desired group by observing the actions of the listener cells (for example, if the group consists of lighting controls, the light flashes). Now using that group ID, the grouping device broadcasts a packet to the group requesting that each cell reply with its cell name until the cell of interest is found. The user selects that name and the grouping device, knowing that cell's ID, can proceed with the group assignment process. If a user elects, the ID of the cell may be verified before proceeding with the grouping procedure. The following procedure is used to verify that the ID is for the target cell. If the selected cell is an announcer, the grouping device prompts the user to activate the announcer by stimulating its input. For example: if the cell is attached to a light switch, the user turns the switch on and off. The grouping device is then able to discover the group address and member number of the cell. If the selected cell is a listener, the grouping device sends packets to the cell (using the group and member numbers, for addressing) commanding it to toggle its output. For example, if the cell controls a light, the light will flash on and off. This allows the user to verify that he has selected the correct cell. 5. Stimulate Announcer.

This method is used in a network in which no group or cell ASCII names have been assigned but announcers and listeners have been assigned. The grouping device sends a packet to all cells in the network commanding each announcer to broadcast a packet containing its ID the next time it is stimulated. The grouping device then prompts the user to stimulate the announcer by activating its sensed device; for instance, turn on a light switch for a light switch announcer. Since the user will stimulate only one announcer, the grouping device will receive only one packet with a cell ID. There is a chance that another announcer cell will be stimulated at the same time. Perhaps someone else throws a light switch or a temperature sensor detects a temperature change. The user may want to verify that the ID received is for the correct cell. To verify that the cell ID is the correct one, the user goes through the announcer stimulation process a second time and verifies that the same results occur. 6. Toggle Listener

This method is used in a network in which no group or cell names have been assigned. The grouping device broadcasts a packet that queries cells that are listeners to reply with their ID. The grouping device needs to limit the number of cells replying so the packet contains an ID bit mask to limit replies to a subset of the possible cell IDs. When the grouping device has developed a list of listener IDs, it allows the user to toggle each listener, causing the listener cell to turn its output on and off. The user continues through the list of listener cells until he observes the target cell toggling its output. The user has then identified the cell to the grouping device and it can proceed with the grouping operation. D. PACKET FORMAT

Each packet transmitted by a cell contains numerous fields. For example, a format used for group announcements is shown in Figure 6. Other packet formats are set forth in Appendix A. Each packet begins with a preamble used for synchronizing the receiving cells' input circuitry (bit synch). The particular preamble code used in the currently preferred embodiment is described as part of the three-of-six combinatorial codes (Figure 9). A flag field of 6 bits begins and ends each of the packets. The flag field code is also described in Figure 9.

As currently preferred, each of the cells reads-in the entire packet, does a cyclic redundancy code (CRC) calculation on the packet except for the contention timer field and compares that result with the CRC field of the received packet. The ALU 1 02 of Figure 1 2 has hardware for calculating the packet CRC and CRC registers 1 30 for storing intermediate results. If the packet CRC cannot be verified for an incoming packet, the packet is discarded. The packet CRC field is 1 6 bits as calculated, then converted into 24 bit fields for transmission in a 3-of-6 code using the encoding of Figure 9. (For the remainder of discussion of packet fields in this section, the field length is described prior to encoding with the 3-of-6 combinatorial codes of Figure 9.) In the currently preferred embodiment the CRC is a CCITT standard algorithm (X^{1 6}+χ ^{1 2} + χ ⁵ + 1).

The system ID is a 32 bit field as currently preferred. The other 1 6 bits of the 48 bit system ID are included in the CRC calculation but not transmitted as part f the packet (Figure 29). The link address field is a 48 bit field. When this field is all zeroes the packet is interpreted as a system wide broadcast which is acted upon by all the cells. For instance, a probe packet has an all zero field for the link address. Group addresses are contained within the link address. For group addresses the first 38 bits are zero and the remaining 10 bits contain the group address. (The cell ID numbers assigned at the factory mentioned earlier range from 1024 to 2⁴⁸ since 2 ¹⁰ addresses are reserved for groups.) The link address, in some cases, is an individual's cell's address. (For example, when a cell is being assigned the task of repeater or listener.)

The contention timer is a 10 bit field with an additional 6 bits for a CRC field (or other check sum) used to verify the 1 0 bits of the timer field. Each cell which repeats a packet operates upon this field if the cell must wait to transmit the packet. If packets are being transmitted by other cells a cell must wait to transmit its packet, the time it waits is indicated by counting down the contention timer field. The rate at which this field is counted down can be programmed in a cell and this rate is a function of the type of network. The field starts with a constant which may be selected by the type of network. Each cell repeating the packet counts down from the number in the field at the time the packet is received. Therefore, if a packet is repeated four times and if each of the four ceils involved wait for transmitting, the number in the contention field reflects the sum of the times waited subtracted from a constant (e.g., all ones). When the contention timer field reaches all zeroes, the cell waiting to transmit the packet discards the packet rather than transmit it. This prevents older packets from arriving and being interpreted as being a new packet. As mentioned, the contention timer has its own 6 bit CRC field. If the contention timer field were included in the packet CRC, the packet CRC could not be computed until a packet could actually be transmitted. This would require many calculations in the last few microseconds before a transmission. To avoid this problem a separate CRC field is used for the contention timer field. If the contention timer field cannot be verified by its 6 bit CRC, the packet is discarded. The hop count field records the number of hops or retransmissions that a packet takes before arriving at its destination. This 4 bit field starts with a number which is the maximum number of retransmissions allowed for a particular packet and is decremented by each cell repeating a packet. For example, in a packet originated by a group announcer the starting "hop" count is the maximum number of retransmissions that the packet must undergo to reach all of the cells in a group. When this field becomes ail zeroes, the packet is discarded by the cell, rather than being retransmitted Therefore, 1 6 hops or retransmissions is the limit as currently implemented.

The link control field provides the link protocol and consists of 8 bits. This field is discussed in a subsequent section covering other layers of the protocol. The random/pseudo random number field contains an 8 bit random number which is generated for each packet by the cell originally transmitting the packet. This number is not regenerated when a packet is repeated. This number is used as will be explained in conjunction with Figure 8 to limit rebroadcasting of probe packets; it also may be used in conjunction with encryption where the entire packet is to be encrypted. The network control field (4 bits) indicates routing type or packet type, for instance, network control, group message, probe message, etc.

The source address field (variable size) contains, by way of example, the 48 bit ID number of the cell originating a packet. For a probe packet this field contains the ID number of the announcer. For an acknowledgement the field contains the ID of the listener. For a packet addressed to a group, this field contains the source cell's group member number. The destination fist is described in conjunction with Figure

7.

The message field is variable in length and contains the particular message being transmitted by the packet. Typical messages are contained in Appendix B. In the case of a probe packet the field includes the routing; that is, each cell repeating includes its ID number to this field. The messages, once a group is formed, will, for instance, is used by announcer 60 to tell listener 65 to turn-on a light, etc.

The encryption field, when used, contains 1 6 bits used to verify the authenticity of an encrypted packet typically this portion of a packet is not changed when a packet is repeated. Well-known encryption techniques may be used. The bracket 99 of Figure 6 represents the portion of a packet which remains unaltered when a packet is repeated. These fields are used to limit repeating as will be described in conjunction with Figure 8. The destination list field of the packet of Figure 6 is shown in Figure 7. The destination list begins with a 4 bit field which indicates the number of members in a group designated to receive a message in the packet. Therefore the packet can be directed to up to 1 6 members of a group. The number of each of the members within the group is then transmitted in subsequent 8 bit fields. The group number contained in the link address and member number contained in the destination list forms an address used to convey messages once the group is formed. If the destination number is zero, the packet is addressed to all members of the group. For some packet types this field contains the ID of the receiving cell (see Appendix A).

E. MECHANISM FOR PREVENTING REBROADCASTING OF

CERTAIN PACKETS

As previously mentioned, the probe packets are repeated only once by each of the cells after the packet is initially broadcast. A special mechanism programmed into each of the cells allows the cells to recognize packets which it has recently repeated.

First, it should be recalled that as each cell transmits, or retransmits a packet, it calculates a packet CRC field which precedes the end flag. For packets that are repeated, a new CRC is needed since at least the hop count will change, requiring a new packet CRC field for the packet. This CRC field is different from the CRC field discussed in the next paragraph. As each packet requiring repeating is received, a repeater

CRC number is calculated for the fields extending from the beginning of the link control to the end of the destination list as indicated by bracket 99 of Figure 6. As a cell rebroadcasts a packet it stores the 1 6 bit repeater CRC results in a circular list of such numbers if the same number is not already stored.

However, the packet is repeated only if the circular list does not contain the repeater CRC results calculated for the field 99.

Therefore, as each packet is received which requires repeating, the CRC is computed for the field 99. This is shown by block 73a of Figure 8. This number is compared with a list of 8 numbers stored within the RAM contained within the cell indicated by block 73b. If the number is not found within the stored numbers, the new repeater CRC results are stored as indicated by block 73c and the packet is repeated. On the other hand, if the number is found then the packet is not repeated. As presently implemented, 8 numbers are stored in a circular list, that is, the oldest numbers are discarded as new ones are computed.

The use of the repeater CRC calculation associated with the field 99 and the use of the circular list will prevent repeating of a previously rebroadcasted packet. Note that even if an announcer continually rebroadcasts the same sequence of messages, for example, as would occur with the continuous turning on and turning off of a light, a cell designated as a repeater will rebroadcast the same message since the packet containing messages appears to be different. This is true because the random number sent with each of the identical messages will presumably be different. However, in the instance where a cell receives the same message included within the same field 99 (same random number), the packet with its message will not be rebroadcast. This is particularly true for probe packets. Thus, for the establishment of groups discussed above, the broadcast probe packets quickly "die out" in the network, otherwise they may echo for some period of time, causing unnecessary traffic in the network.

F. THREE-OF-SIX-COMBINATORIAL CODING In many networks using the synchronous transmission of digital data, encoding is employed to embed timing information within the data stream. One widely used encoding method is Manchester coding. Manchester or other coding may be used to encode the packets described above, however, the coding described below is presently preferred. A three-of-six combinatorial coding is used to encode data for transmission in the presently preferred embodiment. All data is grouped into 4 bit nibbles and for each such nibble, six bits are transmitted. These six bits always have three ones and three zeroes. The transmission of three ones and three zeroes in some combination in every six bits allows the input circuitry of the cells to quickly become synchronized (bit synch) and to become byte synchronized as will be discussed in connection with the I/O section. Also once synchronized (out of hunt mode) the transitions in the incoming bit stream are used to maintain synch. The righthand column of Figure 9 lists the 20 possible combinations of 6 bit patterns where 3 of the bits are ones and 3 are zeroes. In the lefthand column, the corresponding 4 bit pattern assigned to the three-of-six pattern is shown. For example, if the cell is to transmit the nibble 01 1 1 , it is converted to the bit segment 01 001 1 before being transmitted. Similarly, 0000 is converted to 01 1 01 0 before being transmitted. When a cell receives the 6 bit patterns, it converts them back to the corresponding 4 bit patterns.

There are 20 three-of-six patterns and only 1 6 possible 4 bit combinations. Therefore, four three-of-six patterns do not have corresponding 4 bit pattern assignments. The three-of-six pattern 0101 01 is used as a preamble for all packets. The flags for all packets are 1 01 01 0. The preamble and flag patterns are particularly good for use by the input circuitry to establish data synchronization since they have repeated transitions at the basic data rate. The two three-of-six patterns not assigned can be used for special conditions and instructions.

Accordingly, a cell prepares a packet generally in integral number of bytes and each nibble is assigned a 6 bit pattern before transmission. The preamble and flags are then added. The circuitry for converting from the 4 bit pattern to the 6 bit patterns and conversely, for converting from the 6 bit patterns to the 4 bit patterns is shown in Figures 14 and 1 5. I I I . COMMUNICATION AND CONTROL CELL

A. Overview of the Cell

Referring to Figure 10, each cell includes a multiprocessor 100, input/output section 1 07-1 1 0, memory 115 and associated timing circuits shown specifically as oscillator 112, and timing generator 111. Also shown is a voltage pump 116 used with the memory 115. This cell is realized with ordinary integrated circuits. By way of example, the multiprocessor 100 may be fabricated using gate array technology, such as described in U.S. Patent 4,642,487. The preferred embodiment of the cell comprises the use of CMOS technology where the entire cell of Figure 10 is fabricated on a single silicon substrate as an integrated circuit. (The multiprocessor 1 00 is sometimes referred to in the singular, even though, as will be described, it is a multiprocessor, specifically four processors.)

The multiprocessor 100 is a stack oriented processor having four sets of registers 101, providing inputs to an arithmetic logic unit (ALU) 102. The ALU 1 02 comprises two separate ALU's in the presently preferred embodiment. The memory 1 1 5 provides storage for a total of 64KB in the currently preferred embodiment, although this particular size is not critical. One portion of the memory is used for storing instructions (ROM code 1 1 5a). The next portion of the memory is a random-access memory 1 1 5b which comprises a plurality of ordinary static memory cells (dynamic cells can be used). The third portion of the memory comprises an electrically erasable and electrically programmable read-only memory (EEPROM) 1 1 5c. In the currently preferred embodiment, the EEPROM 1 1 5c employs memory devices having floating gates. These devices require a higher voltage (higher than the normal operating voltage) for programming and erasing. This higher potential is provided from an "on-chip" voltage pump 116. The entire address space for memory 115 addressed through the ALU 102a which is one part of the ALU 1 02.

The ROM 1 1 5a stores the routines used to implement the various layers of the protocol discussed in this application. This ROM also stores routines needed for programming the EPROM 1 1 5c. The application program for the cell is stored in ROM 1 1 5a and, in general, is a routine which acts as a "state machine" driven by variables in the EEPROM 1 15c and RAM 1 1 5b. RAM 1 1 5b stores communications variables and messages, applications variables and "state machine" descriptors. The cell ID, system ID and communications and application parameters (e.g., group number, member number, announcer/repeater/listener assignments) are stored in the EEPROM 1 1 5c. The portion of the EEPROM 1 1 5c storing the cell ID is "write-protected" that is, once programmed with the cell ID, it cannot be reprogrammed The input/output section of the cell comprises four subsections 107, 108, 109 and 110. Three of these subsections 107, 108 and 109 have leads 103, 104, and 105 respectively for communicating with a network and/or controlling and sensing devices connected to the cell. The remaining subsection 1 1 0 has a single select pin 1 06 which can be used to read in commands such as used to determine the cell's ID. As presently implemented, the subsection 110 is primarily used for timing and counting. The input/output section is addressed by the processor through a dedicated address space, and hence, in effect appears to the processor as memory space. Each I/O subsection can be coupled to each of the subprocessors. This feature, along with the multiprocessor architecture of processor 100, provides for the contintrous (non-interrupted) operation of the processor. The I/O section may be fabricated from well-known circuitry; the presently preferred embodiment is shown in Figures 1 7 through 23.

The cell of Figure 10 also includes an oscillator 112 and timing generator 111, the latter provides the timing signals particularly needed for the pipelining shown in Figure 13. Operation at a 16mHz rate for the phases 1-4 of Figure 13 is currently preferred, thus providing a 4mHz minor instruction cycle rate. Other well-known lines associated with the cell of Figure 10 are not shown (e.g., power). All of the cell elements associated with Figure 1 0 are, in the preferred embodiment, incorporated on a single semiconductor chip, as mentioned.

B. PROCESSOR The currently preferred embodiment of the processor 1 00 is shown in Figure 12 and includes a plurality of registers which communicate with two ALU's 102a and 102b. (Other processor architectures may be used such as one having a "register" based system, as well as other ALU and memory arrangements.) The address ALU 102a provides addresses for the memory 115 and for accessing the 1/0 subsections. The data ALU 102b provides data for the memory and I/O section. The memory output in general is coupled to the processor registers through registers 1 46 to DBUS 223.

The 16-bit ABUS 220 provides one input to the address ALU 102a. The base pointer registers Il8, effective address registers II9 and the instruction pointer registers 120 are coupled to this bus. (In the lower righthand corner of the symbols used to designate these registers, there is shown an arrow with a designation "x4". This is used to indicate that, for example, the base pointer register is 4 deep, more specifically, the base pointer register comprises 4 16-bit registers, one for each processor. This is also true for the effective address registers and the instruction pointer registers.) The BBUS 221 provides up to a 12 bit input to the ALU 102a or an 8 bit input to the data ALU 102b through register 1 42. The 4 deep top of stack registers 122, stack pointer registers 123, return pointer registers 124 and instruction registers 125 are coupled to the BBUS.

The CBUS 222 provides the other 8-bit input to the ALU 102 through register 143. The CBUS is coupled to the instruction pointer registers 120, the 4 deep top of stack registers 122, the four carry flags 129, and the 4 deep CRC registers 130 and the 4 deep next registers 131. The MBUS, coupled to the output of the memory, can receive data from the output of the ALU 102b through register 145b, or from the memory or I/O sections (1 07-1 1 0). This bus through register 146 and the DBUS 223 provides inputs to registers 118, 119, 120, 122, 123, !24, 125, 130, 131 and to the carry flags 129. There is a 16-bit path 132 from the output of the address ALU 102a to the registers 120. The ALU 102b includes circuitry for performing CRC calculations. This circuitry directly connects with the CRC registers 130 over the bidirectional lines 133. The top of stack registers 122 are connected to the next registers 13I over lines 138. These lines allow the contents of register 122 to be moved into registers 131 or the contents of register 13I to be moved into registers 122. As currently implemented, a bidirectional, (simultaneous) swap of data between these registers is not implemented. Four bits of data from the output of the memory may be returned directly either to the instruction pointer registers 120 or the instruction registers 125 through lines 139.

The pipelining (registers 141 ,142, 143, 1 45 and 146) of data and addresses between the registers, ALU, memory and their respective buses is described in conjunction with Figure 13. The data in any one of the stack pointer registers 123 or any one of the return pointer registers 124 may be directly incremented or decremented through circuit 127.

Both ALU's 102a and 102b can pass either of their inputs to their output terminals, can increment and can add their inputs. ALU 102b in addition to adding, provides subtracting, shifting, sets carry flags 1 24 (when appropriate), ANDing, ORing, exclusive ORing and ones complement arithmetic. The ALU 102b in a single step .also can combine the contents of next registers 1 31 and CRC registers 130 (through paths 222 and 133) and combine it with the contents of one of the top of stack registers 1 22 to provide the next number used in the CRC calculations. Additionally, ALU 102b performs standard shifting and provides a special nibble feature allowing the lower or higher four bits to be shifted to a higher or lower four bits, respectively. Also, ALU 1 02b performs a 3-of-6 encoding or decoding described in Section F. In the preferred embodiment with a single semiconductor chip for a cell there are basic contact pads on the die for power and ground and all the I/O pins A and B and the "read only" pin 1 06 (subsections 1 07, 1 08, 1 09 and 1 1 0, Figure 1 2). These contact pads are used for attachment to package pins for a basic inexpensive package. In addition to the basic contact pads additional pads in the presently preferred embodiment will be provided with connections to the ADBUS 224 and the MBUS 225 of Figure 12. One control contact pad may be provided to disable internal memory. By activating the control contact the internal memory is disabled and the data over ADBUS and MBUS is used by the processors. This allows the use of a memory that is external to the cell. It is assumed that the additional contact pads may not be available for use when the cell is in an inexpensive package. These additional contacts may be accessed by wafer probe contacts or from pins in packages that have more than the minimum number of pins. The cell as manufactured requires an initialization program.

At wafer probe time the external memory is used for several purpose, one or which is to test the cell. Another use is to provide a program to write the cell ID into the EEPROM during the manufacturing process. Any necessary EEPROM instructions to allow power up boot when the cell is later put in use may be added at this time. Initialization programs and test programs are well-known in the art. C. PROCESSOR OPERATION In general, memory fetches occur when the ALU 102a provides a memory address. The memory address is typically a base address or the like on the ABUS from one of the base points in registers 118, effective address registers 1 1 9 or instruction pointer register 120 combined with an offset on the BBUS from the stack pointer register 123, return pointer register 124, top of stack registers 1 22 or the instruction registers 1 25.

Calculations in the ALU 102b most typically involve one of the top of stack registers 1 22 (BBUS) and the next registers 1 31 (CBUS) or data which may be part of an instruction from one of the instruction registers 125.

While in the presently preferred embodiment, the processor operates with the output of the memory being coupled to the DBUS 223 through register 146, the processor could also be implemented with data being coupled directly to the input of ALU 102b. Also, the function performed by some of the other registers, such as the effective address registers 119 can be performed by other registers, although the use of the effective address registers, and for example, the CRC registers, improve the operation of the processor. In general, for memory addressing, a base pointer is provided by one of the registers 1 1 8, 1 1 9 or 1 20 with an offset from one of registers 1 22, 1 23, 1 24 or 1 25. The address ALU 1 20a provides these addresses. Also, in general, the ALU 1 20b operates on the contents of the top of stack and next register; there are exceptions, for example, the instruction register may provide an immediate input to the ALU 1 02b. Specific addressing and other instructions are described below.

D. MULTIPROCESSOR OPERATION The processor is effectively a multiprocessor (four processors) because of the multiple registers and the pipelining which will be described in conjunction with Figure 13. As mentioned, one advantage to this multiprocessor operation is that interrupts are not needed, particularly for dealing with input and output signals. The multiprocessor operation is achieved without the use of separate ALUs for each processor. In the currently preferred embodiment, economies of layout are obtained by using two ALUs, (102a and 102b) however, only one of the ALUs operates at any given time. (Note the BBUS provides an input to both ALUs.) Therefore, the multiprocessor operation of the present invention may be obtained using a single ALU. The processing system has four processors sharing an address ALU, a data ALU and memory. A basic minor cycle takes four clock cycles for each processor. The ALUs take one clock cycle and the memory takes one clock cycle. The minor cycles for each processor are offset by one clock cycle so that each processor can access memory and ALUs once each basic minor cycle. Since each processor has its own register set it can run independently at its normal speed. The system thus pipelines four processors in parallel. Each register of Figure 12 is associated with one of four groups of registers and each group facilitates the multiprocessor operation and is associated with a processor (1 -4) of Figure 1 3. Each of the four groups includes one base pointer register, effective address register, instruction pointer register, top of stack register, stack pointer register, return pointer register, instruction register, CRC register, next register, and a carry flag. Each related group of registers corresponds to one of the four processors. Each processor executes instructions in minor cycles, each minor cycle consisting of four clock cycles. During the first clock cycle a processor will gate the appropriate registers onto the ABUS, BBUS and CBUS. In the next clock cycle the ALUs will be active generating data from their inputs of the ABUS, BBUS and CBUS. Memory or I/O will be active during the third clock cycle, with the address coming from the ALU 1 02a and data either being sourced by memory or the ALU 1 02b. The fourth and final clock cycle will gate the results from memory or the ALU 1 02b into the appropriate register via the DBUS.

A processor can be viewed as a wave of data propagating through the sequence described above. At each step the intermediate results are clocked into a set of pipeline registers. By using these pipeline registers it is possible to separate the individual steps in the sequence and therefore have four steps executing simultaneously. The four processors can operate without interfering with one another even though they share the ALUs, memory, I/O and many control circuits.

The control of a processor including the pipelining is best understood from Figure 1 1 . For each processor there is a 3 bit counter and an instruction register. These are shown in Figure 1 1 as counters 1 37a through 1 37d, each of which is associated with one of the instruction registers 1 25a through 1 25d, respectively. Each of the instruction registers is loaded through the DBUS. As an instruction register is loaded, the instruction is coupled to a PLA 21 2. This PLA determines from the instruction how many minor cycles are required to execute the instruction and a 3 bit binary number is then loaded into the counter 1 1 3a or 1 1 3b or 1 1 3c or 1 1 3d, associated with the instruction register 125a, or 1 25b, or 1 25c or 1 25d being loaded. For instance, for a CALL instruction loaded into instruction register 1 25c, the binary number 01 0 (indicating three minor cycles) is loaded into counter 1 37c. (Up to 8 minor cycles can be used for a given instruction, however, only up to 6 minor cycles are used for any of the instructions in the currently preferred embodiment.) The count value "000" is used to cause a new instruction to be fetched. The count (e.g., 3 bits) in a counter and the instruction (e.g., 1 2 bits) in its associated instruction register from a 1 5 bit input to the PLA 1 36. These 1 5 bit inputs from each of the respective four sets of count registers and four sets of instruction registers are sequentially coupled to the PLA 1 36 as will be described. The output of the PLA controls the operation of the processors. More specifically: lines 21 3 control data flow on the ABUS, BBUS and CBUS; lines 21 4 control the ALU 1 02; lines 21 5 control the memory; (and, as will be described later I/O operation of subsections 1 07, 1 08, 1 09 and 220) and lines 21 6 control data flow on the DBUS. The specific outputs provided by the PLA 1 36 for a given instruction is best understood from the instructions set, set forth later in this application. The action taken by the processors to execute each of the instructions is described with the instruction set.

The outputs from the PLA on lines 21 3 are coupled directly to the devices controlling data flow on the ABUS, BBUS, and CBUS. The signals controlling the ALU are coupled through a one clock phase delay register 217 before being coupled to the ALU via the lines 214. Since all the registers 217 are clocked at the same rate, the register 21 7 performs delay functions as will be described. Those signals from the PLA 1 36 used for memory control are coupled through two stages of delay registers 217 before being coupled to the memory, thus the signals on lines 21 5 are delayed for two clock phases related to the signals on lines 21 3. The control signals for the DBUS after leaving the PLA 1 36 are coupled through 3 sets of delay registers 217 before being coupled to the lines 21 6 and therefore are delayed three clock phases related to those on lines 21 3. The registers 21 7 are clocked at a 6mHz rate, thus when the PLA 1 36 provides output control signals for a given instruction (e.g., contents of instruction register 1 25a) the control signals during a first clock phase are coupled to lines 21 3, during a second clock phase, lines 214; during a third clock phase, 21 5; and during a fourth clock phase to lines 21 6. During the first clock phase of each instruction cycle, the contents of the counter 1 37a and the instruction register 1 25a are coupled to the PLA 1 36. During the second clock phase, the contents of the counter 1 37b and instruction register 1 25b are coupled; to the PLA 1 36 and so on for the third and fourth clock phases.

Assume now that instructions have been loaded into the instruction registers 125a through 125d and the counters 1 37a through 1 37d have been loaded with the corresponding binary counts for the minor cycles needed to perform each of the instructions. For example, assume that register 1 25a is loaded with a CALL instruction and that 01 0 has been loaded into counter 1 37a. During a first instruction minor cycle, 01 0 and the 1 2 bit instruction for CALL are coupled to the PLA 1 36. From this 1 5 bit input PLA 1 36 provides at its output all the control signals needed to complete the first minor cycle of the CALL instruction (e.g., four clock phases) for the ABUS, BBUS CBUS, the ALU, the memory and the DBUS. Since the system uses pipelining multiprocessing, the control signals on lines 21 3 used to carry out the first clock phase of the CALL instruction which is the inputs to the ALUs. (During this first clock phase the other control lines are controlling the ALU, the memory and the DBUS of other processors, for different instructions in the pipelines.) During phase 2, the count in counter for 1 37b and the instruction in register 1 25b are coupled to the PLA 1 36. During phase 2, the signals on lines 21 3 now control the ABUS, BBUS and CBUS inputs to the ALUs for the second processor to carry out the instruction contained in register 1 25b. During this second clock phase, the signals on lines 214 control the first processor and the ALU to perform the functions needed to carry out the second clock phase of the CALL instruction contained in register 1 25a. (Note a delay equal to one phase was provided by register 217.) Similarly, during the third phase, the signals on lines 21 3 control the ABUS, BBUS, and CBUS for the third processor to carry out the instruction contained in register 1 25c; the signals on lines 214 control the ALU to carry out the instruction contained in register 1 25b, and the signals on lines 21 5 control the memory to carry out the instructions in register 1 25a for the first processor. And, finally, during the fourth clock phase, the instruction from register 1 25d, along with the count in counter 1 37d are coupled to the PLA 1 36. The signals on lines 21 3 control the ABUS, BBUS and CBUS to carry out the instruction contained within register 1 25d fourth processor; the signals on lines 214 control the ALU to carry out the instruction in register 1 25c for the third processor; the signals on lines 21 5 control the memory to carry out the instruction in register 1 25b for the second processor; and the signals on lines 21 6 control the DBUS to carry out the instruction in register 1 25a for the first processor.

After four cycles of the 1 6mHz clock the count in register 1 37a decrements to 001 . Each register is decremented on the clock cycle following the use of the contents of the counters contained by the PLA 1 36. The input to the PLA 1 36 thus changes even though the instruction within register 1 25a is the same. This allows the PLA 1 36 to provide new output signals needed for the second minor cycle of the CALL instruction. These control signals are rippled through the control through the control lines 21 3, 21 4, 21 5 and 21 6 as described above. When the count in a counter reaches 000, this is interpreted as an instruction fetch for its associated processor. Therefore, each of the four processors may simultaneously execute an instruction where each of the instructions has a different number of cycles. The control signals reaching the imaginary line 21 9 for any given clock cycle represent control signals for four different instructions and for four different processors. For example, the control signals associated with the first processor during a first cycle appear on lines 21 3; during a second cycle on lines 214; during a third cycle on lines 21 5; and during a fourth cycle on lines 21 6. The control signals needed by the second processor follow behind; those needed by the third and fourth processors following behind those used by the second processor. The pipelining of the signals is illustrated in Figure 1 3.

The multiprocessor operation of the processor 100 of Figure 10 is shown in Figure 1 3 as four processors, processors 1, 2, 3 and 4. Each one of the groups of registers is associated with one of the processors. The four phases of a single instruction cycle are shown at the top of Figure 13. In Figure 1 3, registers 1 01 are used to indicate that the contents from the specific registers called for in an instruction are placed on the ABUS, BBUS and CBUS. The registers are 1 1 8, 1 19 and 120 on the ABUS; 1 22, 1 23, 1 24 and 1 25 on the BBUS; 1 20, 122, 1 29, 1 30 and 131 on the CBUS.

During a first phase, signals previously stored in the group 1registers (e.g., two of them) are gated from the registers onto the ABUS, BBUS and CBUS. While this is occurring, signals associated with the group 2 registers are gated from the registers 1 41 , 142, 1 43 into the ALU 1 02a and 1 02b. This is shown in Figure 1 3 as processor 2 under the first phase column. Simultaneous signals are gated from registers 145a and 145b into the memory for group 3 registers for processor 3. And, finally, during this first phase, signals associated with the group 4 registers are gated from registers 1 46 onto the DBUS. During the second phase, signals associated with a group 1 registers are coupled from the ALU to registers 1 45. The data associated with group 2 registers are coupled to memory. The data associated with the group 3 registers is coupled from the register 146 onto the DBUS. Those associated with the group 4 registers are gated onto the ABUS, BBUS and CBUS . And, similarly, during the third and fourth phase of each instruction cycle, this pipelining continues as shown in Figure 1 3, thus effectively providing four processors.

E. PROCESSOR INSTRUCTIONS

In this section each instruction of the processor is set forth, along with the specific registers and memory operations. Lower case letters are used below to indicate the contents of a register. For example, the contents of the instruction register are shown as "ip". The registers and flags are set forth below with their correlation to Figure 1 2.

FIGURE 12 IDENTIFICATION ip instruction pointer (14 bits) 120

(fixed range of 0000 - 3FFF) (not accessible to ROM based programs)

ir instruction register (12 bits) 125

(not accessible to ROM based programs)

bp base page pointer (14 bits) 118

(fixed range of 8000 -FFFF) (write only)

ea effective address pointer (16 bits) 119 (not accessible to ROM based programs)

sp data stack pointer (8 bits) 123

(positive offset from bp, grows down)

rp return stack pointer (8 bits)

(positive offset from bp, grows up) 124 to s top of data stack (8 bits) 1 22

next item below top of data stack (8 bits) 1 31

c rc used as scratch or in 1 30

CRC calculations (8 bits)

f lag s carry flags, (1 bit) 1 29 processor ID (2 bits)

The top element of the return stack is also addressable as a register, even though it is physically located in RAM.

Instruction Table

CALL 1aaa aaaa aaaa Subroutine call

CALL lib 0000 aaaa aaaa Library call

BR 0010 1aaa aaaa Branch

BRZ 0010 00aa aaaa Branch on TOS==0 BRC 0010 11aa aaaa Branch on Carry set

CALL interseg 0011 LLLL LLLL (Subroutine)

0000 hhhh hhhh Two word instruction

LIT 0101 1ffh bbbb Constant op TOS

LDC 0101 111h bbbb Load Constant

ALU 0101 00ef ffff Top of Stack and NEXT

RET 0101 0011 1101 Return or Bit set in other instruction

IN, OUT 0100 0wrr rrrr Read/Write I/O Register

LD,ST bp+a 0100 1waa aaaa Load, Store

LD,ST (bp+p)+a 011p pwaa aaaa Load, Store

LDR,STR r 0101 01 Ow rrrr Load, Store CPU reg For each instruction, the operation, encoding and timing are set below in standard C language notation. CALL Call Procedure

Operation:

*rp++ = lowbyte (ip); *rp++ = hibyte (ip); ip = dest;

Encoding:

intra-segment: 1aaa aaaa aaaa dest = ip + a + 1; /* displacement a is always negative */

inter-segment:

001 1 LLLL LLLL 0000 HHHH HHHH

dest = H:L; /* 16 bit absolute address */ library:

0000 aaaa aaaa dest = 0x8000+*(0x8001 + a); /* table lookup call */

Timing:

CALL type #clocks specific memory operation

intra-seg

2 *rp++ = lobyte (ip) 1 *rp++ = hibyte (ip)

0 ir = *(ip = *dest)

interseg

4 lobyte (ea) = *ip++

3 hibyte (ea) = *ip

2 *rp++ = lobyte (ip) 1 *rp++ = hibyte (ip)

0 ir = *(ip = *dest)

library 3 *rp++ - lobyte (ip)

2 *rp++ = hibyte (ip) 1 ip = dest

0 ir = *ip BR Branch always

Operation: ip = dest;

Encoding:

0010 1 aaa aaaa

dest = ip + a + 1 ; /* displacement a is sign extended */

Timing:

#clocks specific memory operation

1

0 ir = *(ip = dest) BRC Branch on carry

Operation:

if ( CF ) ip = dest; else ip++;

Encoding:

001 0 01 aa aaaa dest = ip + a + 1 ; /* a is sign extended */ Timing:

#clocks specific memory operation 1

0 ir = *(ip = dest) or 0 ir = *(++ip);

BRZ Branch on TOS==0

Operation:

if (tos==0, tos=next, next= *(++sp) ) ip = dest; else ++ip;

Encoding:

001 0 OOaa aaaa

dest = ip + a + 1; /* displacement a is sign extended */

Timing:

#clocks specific memory operation

2 1 tos = next; next = *(++sp);

0 ir = *(ip = dest) or

0 ir = *(++ip)

LDR Move register to TOS (includes certain indirect, indexed memory reference)

Operation:

*(sp~) = next; if (reg) { next = tos; tos = reg } else { next = bp+TOS or next = (bp+2p)+TOS } Encoding:

01 01 01 00 rr r r reg = r /* see table */ Timing:

#clocks specific memory operation (if (bp+p)+TOS) 5

4 lobyte(ea) = *(bp+2p) 3 hibyte(ea) =*(bp+2p+1) (if reg, bp+TOS) 3

2 *sp - - = next if (reg) next = tos; 1 if (reg) tos = reg else next=bp+TOS, ea+TOS 0 ir = *(++ip) STR Store TOS. to register

(includes certain indirect, indexed memory reference) Operation: if (reg) { reg = tos; tos = next; } else { bp+TOS = next or (bp+2p)+TOS - next } next = *(++sp); Encoding:

01 01 01 01 rrrr reg = r /* see table */

Timing:

#clocks specific memory operation

(if (bp+p)+TOS) 5

4 lobyte(ea) = *(bp+2p) 3 hibyte(ea) =*(bp+2p+1) if (reg, bp+TOS) 3

2 if (reg) reg = tos; else bp+TOS, ea+TOS=next 1 if (reg) tos = next; next = *(++sp);

0 ir - *(++ip); Register assignments

0000 Flags CF × ID1 ID0

0001 CRC low byte (high byte in TOS)

001 0 lowbyte (bp) /* write */ next ("OVER" instruction) /* read */ 001 1 highbyte (bp) /* write */ tos ("DUP" instruction) /* read */

01 00 sp

01 01 rp

01 1 0 see RPOP, RPUSH

01 1 1 *(bp+TOS) /* indexed fetch, store

1 000 *(*(bp+0)+TOS) /* indexed indirect */

1 001 Y(bp+2)+TQS) /* indexed indirect */ 1 01 0 *(*(bp+4)+TOS) /* indexed indirect */

1 01 1 *(*(bp+6)+T0S) /* indexed indirect */

RPOP pop return stack

Operation:

*(sp--) = next; next = tos; tos = *rp - -;

Encoding:

01 01 01 00 1 1 1 0

Timing:

#clocks specific memory operation 2 *sp-- = next next = tos; 1 tos = *rp --;;

0 ir = *(++ip)

RPUSH push tos onto return stack

Operation:

*(++rp)=tos; tos = next; next = *(++sp);

Encoding:

01 01 01 01 1 1 1 0

Timing:

#clocks specific memory operation 2 *(++rp) = tos; 1 tos = next; next = *(++sp); 0 ir = *(++iρ) IN Move I/O register to TOS

Operation:

*(sp— ) = next; next = tos; tos = reg;

Encoding:

01 00 00 r r rrrr

Timing:

#clocks specific memory operation

3

2 *sp - - = next next - tos; 1 tos - reg ;

0 ir = *(++ip);

OUT Store TOS to I/O register

Operation: reg = tos; tos = next; next - *(++sp);

Encoding:

01 00 01 r r rrr r

Timing:

#clocks specific memory operation

3

2 reg = tos; 1 tos = next; next = *(++sp); ir = *(++ip);

LDC load cons

Operation:

*sp-- = next; next = tos; tos = constant;

Encoding:

01 01 1 1 1 H bbbb

if (H==0) constant = 0000:bbbb; else constant = bbbb:0000 Timing:

#clocks specific memory operation 3

2 *(sp - -) = next; next = tos; 1 tos = constant; 0 ir = *(++ip)

LD (bp+a) load from base page

Operation:-

*sp-- = next next = tos tos = *(bp+source);

Encoding:

01 00 1 0aa aaaa source = aa aaaa

Timing:

#clocks specific memory operation

3 2 *sp - - = next; next = tos; 1 tos = *(bp+source);

0 ir = *(++ip)

LD (bp+p)+a load indirect ( TOS with byte addressed by pointer at bp+offset then indexed by TOS)

Operation:

*sp - - = next; next = tos tos = T(bp+2p)+offset);

Encoding:

01 1 p p0aa aaaa offset - aa aaaa

Timing:

#clocks specific memory operation

4 lobyte(ea) = *(bp+2p) 3 hibyte(ea) =*(bp+2p+1) *sp - - = next; next = tos; 1 tos=*(ea+offset) 0 ir - *(++ip)

ST (bp+a) store into base page

Operation:

*(bp+dest) = tos tos - next; next = *(++sp) Encoding:

01 00 1 1 aa aaaa dest = aa aaaa

Timing:

#clocks specific memory operation

2 *(bp+dest) = tos; 1 tos = next; next = *(++sp); 0 ir = *(++ip)

ST (bp+p)+a store indirect

( TOS into byte addressed by pointer at bp+2p offset by a)

Operation:

*(*(bp+2p)+offset)=tos; tos = next; next = *(++sp)

Encoding:

01 1 p pl aa aaaa offset = aa aaaa

Timing:

#clocks specific memory operation 4 lobyte(ea) = *(bp+2p)

3 hibyte(ea) =*(bp+2p+1 )

2 *( ea+off)=tos 1 tos = next; next = *(++sp)

0 ir = *(++ip)

[ ALU Group ]

Operation:

if (r== 1 ) { hibyte(ip) - *rp - - ; lobyte(ip) = *rp - - ; } pipe = tos; /* internal processor pipeline */ tos = tos op next; switch (s) { case 0: next = next; /* typical unary op */ case 1 : next = *(++sp); /* typical binary op */

} Encoding:

01 01 O O rf f f f f op = fffff /* s equal to high order f bit */ s - (1==unary op), (0==binary op)

Op Table:

code operation carry state

00000 tos + next arith carry

00001 tos + next + carry arith carry

00010 next - tos arith borrow

00011 next - tos - carry arith borrow

00100 tos - next arith borrow

00101

00110

00111

01000 tos AND next unchanged

01001 tos OR next unchanged

01010 tos XOR next unchanged

01011

01100 drop unchanged 01101 swap-drop unchanged

01110

01111 CRC step unchanged 10000 asl (TOS) tos7 10001 asr (TOS) 0 10010 rotate left(tos) tos7 10011 rotate right (tos) tos0 10100 tos parity (TOS) 10101 10110 10111 3of6 encode set if not valid

11000 Isl (TOS) 11001 Isr (TOS) 1 1010 shift left by 4 11011 shift left by 4 11100 swap 11101 tos (NOP) 11110 NOT(TOS) 11111 3of6 decode

Timing:

S #cl locks specific memory operation

1 2 (4)

(if r==1) 3 hibyte(ip) = *rp - - ; )

(if r==1 ) 2 lobyte(ip) = *rp - - ; ) 1 tos = alu output 0 ir = *(++ip)

0 3 (5)

(if r==1) 4 hibyte(ip) = *rp - - ; )

(if r== 1) 3 lobyte(ip) = *rp - - ; ) 2 tos = alu output 1 *(++sp) = next 0 ir = *(++ip)

SWAP special case

The exchange of TOS with NEXT is a special case of the ALU ops using the direct data path between TOS and NEXT. The NEXT register receives a of the TOS via a pipeline register, prior to TOS being loaded with the content of NEXT (non-simultaneous transfer).

NOP

Operation:

++ip;

Encoding:

short 001 0 1 000 0000

long 01 01 0001 1 101 Timing:

#clocks specific memory operation

short

(BR+1) 0 ir = *(++ip) long 1 tos - tos 0 ir = *(++ip) RET return from subroutine

Operation:

hibyte(ip) = *rp - - lobyte(ip) = *rp - - ++ip;

Encoding:

01 01 001 1 1 1 01

Timing: #clocks specific memory operation

3 hibyte(ip) = *rp - -

2 lobyte(ip) = *rp - - 1 tos = tos ir = *(++ip)

[ LITERAL Group ]

Operation: tos = tos op constant;

Encoding:

01 01 1 f f H cccc op = ff if (H==0) constant = 0000:cccc else constant = cccc:0000

Op Table:

code operation carry state 00 tos + constant arith carry 01 tos - constant arith borrow 00 tos AND constant 1 1 constant (see LDC)

Timing:

#clocks specific memory operation 2 1 tos = alu output 0 ir = *(++ip)

F. THREE-OF-SIX CIRCUITRY

As previously mentioned, the ALU 1 02b contains means for encoding four bit nibbles into six bit words for transmission

(encoder of Figure 1 4) and for decoding six bit words into the four bit nibbles (decoder of Figure 1 5). Both the encoder and decoder use hardwired logic permitting the conversion to be performed very quickly in both directions. Moreover, there is a circuit shown in Figure 1 6 to verify that each six bit word received by the cell is in fact a three-of-six code, that is, three zeroes and three ones (Figure

9). Referring to Figure 1 4 the register 1 42 is illustrated with four bits of the register containing data D0 through D₃. If the ALU is commanded to encode this data, the resultant six bits will be coupled into the latch register 145b. To obtain the conversion shown in Figure 9, the D₀ bit is directly coupled into first stage of register 145b and becomes E₀, the encoded bit. Also, the bit D₃ is directly coupled into the register and becomes E₅. Each of the remaining bits E₁ through E₄ are provided by the logic circuits 1 53 through 1 50, respectively. Each of these logic circuits are coupled to receive D₀, D ₁, D₂ and D₃. Each logic circuit contains ordinary gates which implement the equation shown within its respective block. These equations are shown in standard "C" language ( "&" = logical AND, " !" = logical NOT, and "|" = logical OR.) These equations can be implemented with ordinary gates. The decoder of Figure 1 5 is shown in a similar format. This time the six bits of the encoded data are shown in register 142. The decoded four bits of data are shown in the register 145. To implement the pattern assignment shown in Figure 9, the E₀ bit is coupled directly to the register 145 and becomes D₀. The E₅ bit is coupled directly to the register145 and becomes the D₃ bit. Logic circuits 1 54 and 1 55 provide the bits D₂ and D₁ , respectively. Circuit 1 54 is coupled to receive the bits E₀ , E₃, E₄ and E₅ while the circuit 1 55 receives E₀, E₁ , E₃, and E₅ (E₂ is not used to provide the D₀ through D₃ bits.) (Some of the six bit patterns are not used and others are used for synchronization and thus do not require conversion into a data nibble.) The circuits 1 54 and 1 55 are constructed from ordinary logic gates and implement the equations shown. The symbol " Λ " represents the exclusive OR function in the equations.

The circuit of Figure 1 6, as mentioned, verifies that the received six bit words do contain three zeroes and three ones. The encoded words are shown coupled from the top of stack register 1 22 into the two full adders, 1 57 and 1 58. These adder stages are contained within the ALU 1 02b. Each adder receives an X, Y and carry input and provides a sum and carry output. These ordinary adder stages are each coupled to receive one bit of the encoded word as shown. (Any coupling of each bit to any input of address 1 57 and 1 58 may be used.) The carry outputs of the adders 1 57 and 1 58 are coupled to the exclusive OR gate 1 59; the sum outputs of the adders 1 57 and1 58 are coupled to the exclusive OR gate 1 60. The output of the gates 1 59 and 1 60 are coupled to the input terminals of an AND gate 1 61 . If the output of this AND gate is in its high state the word in the register 1 02 contains three ones and three zeroes. Otherwise, the output of the gate 1 61 is in its low state (abort condition). The incoming packets are checked to determine that each six bit word is valid, while it is decoded into the four bit nibbles. IV. INPUT/OUTPUT SECTION

A. General

The I/O section includes a plurality of circuit elements such as a ramp generator, counter, comparator, etc., which are interconnected in different configurations under software control. Examples of this are shown below for the analog-to-digital (A to D) and digital-to-analog (D to A) operations. These elements with their software configurable interconnections provide great flexilibity for the cell, allowing it to perform many tasks. The entire I/O section is preferably fabricated on the same "chip" which includes the processor.

B. Buffer Section

As shown in Figure 1 0 and previously discussed, each of the cells includes four input/output I/O subsections; three of the subsections 1 07, 1 08, and 1 09 each have a pair of leads, identified as Pin A and Pin B. The fourth subsection 1 1 0 has a single "read only" pin 1 06. Any of the four subsections can communicate with any of the four subprocessors. As shown in Figure 1 2, this is easily implemented by connecting the address bus (ADBUS) and the memory bus (MBUS) to each of the four I/O subsections. Use of the MBUS through the register 1 46 to the DBUS allows the I/O subsections to communicate with the processor registers.

Each Pin A and Pin B can receive and provide TTL level signals and is tristated. In the currently preferred embodiment, each pin can sink and source approximately 40milliamps (except for pin 1 06). All the Pin A's can be programmed to provide an analog output signal and a digital-to-analog converter is included in three of the I/O subsections 1 07, 1 08 and 1 09 to provide an analog output on Pin B. An analog input signal on any of the Pin B's can be converted to a digital count since three of the I/O subsections include A to D converters coupled to these pins. Each pin pair (Pin A and Pin B) can operate as a differential amplifier for input signals, a differential receiver, and a differential transmitter and a differential voltage comparator. The I/O subsections can be used to perform many different functions, from simple switching to, by way of example, having two pin pairs coupled to drive the windings of a stepping motor. The circuits shown in Figures 1 7-23 are repeated in subsections 1 07, 1 08 and 1 09. Those circuits associated with Pin A and Pin B (such as the buffer sections of Figure 1 7) are not fully contained in the I/O subsection 1 1 0. Only sufficient buffering to allow data to be read on Pin 1 06 is needed.

Referring to the I/O buffer section of Figure 17, outgoing data is coupled to Pin A through the buffer 1 63. Similarly, outgoing data is coupled to Pin B through the buffer 1 64 after the data passes through the I/O control switch 1 65. This outgoing data, by way of example, is coupled to Pin A from the register 206 of Figure 23 through gate 208 of Figure 1 9. The control switch 1 65 is used to enable outputs to Pin A through the buffer 1 63, when enable A (EN.A) is high (line 1 66). Moreover, the switch enables the output to Pin B when enable B (EN.B) is high (line 1 67) and enables outputs to both pins (with the output to Pin B being inverted) when enable RS-485 is high (line 1 68). The outgoing analog signal to Pin A is provided through the switch 1 75 when the enable analog output signal is high. Incoming signals to Pin A are coupled to one input terminal of the differential amplifier 1 69. The other terminal of this signal receives a reference potential (e.g., 2.5 volts). This amplifier also includes the commonly used hysteresis mode to prevent detection of noise. This mode is activated when the enable hysteresis (Pin A) signal coupled to amplifier 1 69 is high. The output of amplifier 1 69 is coupled to a transition detection circuit 1 71 which simply detects each transition, that is, a zero to one, or one to zero.

The inputs to Pin B are coupled to one terminal of a differential amplifier 1 70 which may be identical to amplifier 1 69. The amplifier 1 70 receives the enable hysteresis (Pin B) signal. The other input to amplifier 1 70 (line 1 76) can be coupled to receive one of several signals. It can receive a DC signal used for voltage comparisons, a ramp which shall be discussed later, the signal on Pin A for differential sensing, or a reference potential (e.g., 2.5 volts). The output of the amplifer 170 can be inverted through the exclusive OR gate 177 for some modes of operation. A transition detector 1 72 is associated with the Pin B inputs, again to detect transitions of zero to one or one to zero. C. I/O Counting/Timing

Each of the cells includes a timing generator (RC oscillator) for providing a 1 6mHz signal. This signal is connected to a rate multiplier 178 contained in the I/O section (Figure 1 8). The multiplier 1 78 provides output frequencies to each I/O subsection. This multiplier provides a frequency f₀ equal to:

The loaded value is a 1 6 bit word loaded into a register of a rate multiplier 1 78. The rate multiplier comprises four 1 6-bit registers and a 1 6-bit counter chain. Four logic circuits allow selection of four different output signals, one for each subsection. Two bus cycles (8 bits each) are used to load the 1 6 bit words into the register of the rate multiplier 1 78. As can be seen from the above equation, a relatively wide range of output frequencies can be generated. These frequencies are used for many different functions as will be described including bit synchronization.

The output of the multiplier 1 78 in each of the subsection is coupled to an 8 bit counter 1 79. The counter can be initially loaded from a counter load register 1 80 from the data bus of the processors. This register can, for example, receive data from a program. The count in the counter is coupled to a register 1 81 and to a comparator 1 82. The comparator 1 82 also senses the 8 bits in a register 1 83. The contents of this register are also loaded from the data bus of the processors. When a match between the contents in the counter and the contents of register 1 83 is detected by comparator 1 82; the comparator provides an event signal to the state machine of Figure 1 9 (input to multiplexers 1 90 and 1 91 ). The contents of the counter 1 79 can be latched into register 181 upon receipt of a signal from the state machine (output of the execution register 198 of Figure 19). The same execution register 198 can cause the counter 179 to be loaded from register 180. When the counter reaches a full count (terminal count) a signal is coupled to the state machine of Figure 19 (input to multiplexers 190 and 191).

D. I/O CONTROL AND STATE MACHINE

Referring to Figure 19, the processor MBUS communicates with registers 185 and 186 both of which perform masking functions. Three bits of the register 185 control the selection of one of the five lines coupled to the multiplexer 190; similarly, 3 bits of the register 186 control the selection of one of the five lines coupled to the input of the multiplexer 191. The output of the masking registers 185 and 186 are coupled to a multiplexer 187. The five bits from the multiplexer 187 are coupled to a register 198. Each of these bits define a different function which is, in effect, executed by the state machine. Specifically, the bits control load counter, latch count, enable ramp switch, pulse Pin A,, and pulse Pin B.

The multiplexers 190 and 191 both receive the terminal count signal from counter 179 of Figure 18, the compare signal from comparator 182, the ramp start signal from the ramp generator 200 of Figure 20, and the transition A and B signals from the transition detectors 171 and 172, respectively of Figure 17. The one bit output from each of the multiplexers 190 and 191 is coupled to an OR gate 188. This OR gate is biased in that if an output occurs simultaneously from both multiplexers 190 and 191, priority is given to multiplexer 190. The output of the multiplexer 190 controls the multiplexer 187 with the signal identified as "which event". This signal is also stored in the 3x3 first-in, first-out (FIFO) buffer 199. This signal indicates which MUX 190 or 191 has received an event and this data is stored along with the inputs to Pin A and Pin B (Figure 17) in the FIFO 199.

The state machine for each of the I/O subsections comprises 4 D-type flip-flops connected in series as shown in Figure 19 within the dotted line 189. The flip-flops 194 and 196 receive the 8mHz signal whereas the flip-flops 193 and 195 receive the complement of this timing signal. The clocking signal (CLK) is obtained from the Q output of the flip-flop 194 and is coupled to register 198 and FIFO 199. The clear signal received from the Q terminal of flip-flop 196 is coupled to the register 198. In operation, the masking registers 1 85 and 1 86 are loaded under software control. The bits from register 1 85, for instance, cause the selection of one of the input lines to multiplexer 1 90, for example, terminal count. Then the circuit of Figure 1 9 waits for the signal terminal count. When the signal terminal count occurs the state machine begins operating and the five bits of data from register 1 85 are connected through multiplexer 1 87 into register 1 98. The state machine causes an output to occur on one of the lines from register 1 98 causing, for example, a pulse to be generated on pin A. Similarly, a word in register 1 86 can be used to cause, again by way of example, the counter to be loaded.

The flip-flops 203 and 204 are clocked by the output of register 1 98. These flip-flops allow the output signal to be controlled. The OR gate 208 permits data from a shift register 206 of Figure 23 to be coupled to Pin A. This register is discussed later.

The low order 6 bits of the ADBUS are input to decoders in the I/O subsections 1 07, 1 08, 1 09 and 1 1 0 of Figure 1 2. Two of the bits are used to select a specific I/O element and the rest are decoded to control an operation. The PLA 1 36 of Figure 1 1 has generalized outputs 21 5 connected in parallel to all I/O subsections 1 07, 1 08, 1 09 and 1 1 0 to select the ABUS clock cycle for data to be used for controlling operation of the I/O subsections.

E. ANALOG TO DIGITAL AND DIGITAL TO ANALOG

CONVERSION Referring first to Figure 20, the I/O subsystem includes a ramp generator 200 which continually generates ramps of a known period. The output of the ramp generator is buffered through buffer 201 and selected by switch 202. The switch, as will be described, is selected at some count (time) following the start of each ramp, thereby coupling the same potential to the capacitor 203. This capacitor becomes charged and potential is coupled through buffer 204 to Pin A when the switch 1 75 is closed. (Switch 1 75 is shown in Figure 1 7.) The switch 202, capacitor 203, and buffer 204 act as a sample and hold means. In Figure 21 several of the circuit elements previously described have been redrawn to describe how a digital to analog conversion occurs and to show how the circuit elements of the I/O subsection can be reconfigured through software by the I/O control and state machine of Figure 1 9 to perform different functions.

For a digital to analog conversion an appropriate frequency (f₀) is selected from the rate multiplier 1 78 or counter 1 79 of Figure 1 8, which corresponds to the period of the ramps being generated by ramp generator 200 (Figure 21 ). A digital value which corresponds to the desired output analog signal is loaded into the register 1 83. When a ramp begins the ramp start signal is coupled through the state machine 1 89 of Figure 1 9 (for example, through the multiplexer 1 90) and the flip-flops). This causes the counter 1 79 to be cleared (e.g., all zeroes). The f₀ signal then counts into counter 179. The comparator 1 82 then compares the contents of the counter1 79 with the contents of register 1 83. When the two words are the same, the compare signal is applied through multiplexer 1 91 again causing the state machine to be activated as indicated by "SM₁ " , 1 89 and the switch 202 of the sample and hold means to close. For each ramp generated by the ramp generator, the ramp switch 202 is closed (e.g., for 500 nanoseconds) causing the capacitor 203 to be charged to a DC voltage which corresponds to the digital number placed in register 1 83.

One manner in which the A-D conversion can be performed is shown in Figure 22. The input analog signal is applied to one input terminal of the differential amplifier 1 70. The ramp is applied to the other terminal of the amplifier 1 70. Initially, when the ramp is started, the state machine 1 89 causes the counter 179 to be loaded from register 1 80 (e.g., all zeroes). The counter is clocked at a frequency (f₀) suitable to the period of the ramps. When the transition detection 172 detects that the potential on Pin B and the ramp have the same potential, the state machine 1 89 causes the count in the counter 1 79 to be latched into latch 1 81 . The digital word in latch 1 81 corresponds to the DC potential on Pin B, thereby providing the analog to digital conversion.

F I/O COMMUNICATIONS As previously discussed, for instance, in conjunction with

Figure 1 , each cell can transmit data over communications lines or other links. The cells in a subchannel transmit data at the same rate typically determined by the communications link being employed, for example, 1 0K BPS in a noisy environment such as for power lines. In the currently preferred embodiment, the cells do not have crystal oscillators but rather rely upon RC oscillators. The latter are not particularly stable and frequency variations occur both with temperature and as a result of processing variations. Moreover, there is no synchronization provided between cells, thus, each cell must provide synchronization to the incoming data in order to properly read the data. One feature of all cells is that they detect and store the frequency of the incoming data and when acknowledging a packet they can transmit at the frequency that the original packet was transmitted. This reduces the burden on cells to synchronize when they are receiving an acknowledgement packet. Referring to Figure 23 during the hunt mode, an I/O subsection is hunting for data. During this mode, the rate multiplier provides a frequency (f₀) to the counter 179 and a number is loaded into register 183 from the MBUS. Matches occur and are detected by comparator 182 at a frequency corresponding to the expected incoming data rate. Specifically, the terminal count of counter 179 is synchronized to the transitions. As indicated by the dotted line 201 , the processor continually searches for transitions from the transition detectors 171 and 172 of Figure 17. When transitions occur, the processor determines whether the transitions occurred before or after the terminal count and then adjusts the frequency (f₀) until the terminal count occurs at the same time that the transitions are detected. This frequency is the shifting rate for the shift register 206. (The steps performed by the processor are shown in Figure 23 as blocks 210 and 211.) The number loaded into register 183 provides a phase shift between the time at which transitions occur and the ideal time to shift data in the register 206. This prevents the shifting of data during transitions. Note counter 1 79 is reloaded (e.g., all zeroes) each time it reaches a terminal count.

When bit synchronization occurs, rate needed for the synchronization (1 6 bit word) is stored within the processor memory and used to set the transmit frequency when acknowledging the packet for which the rate was developed. This stored bit rate as discussed later is used in the contention backoff algorithm allowing slot periods (M) to be matched to the last received bit rate.

The comparator output is used as a shift rate for a six bit shift register 206. During the hunt mode, the data from Pin B is continually shifted through register 206. The preamble to a packet as shown in Figure 9 (01 01 01 -bit synch) is shifted along the shift register 206 and the shifting rate adjusted so that synchronization/lock occurs. When the packet beginning flag appears (nibble synch-1 01 01 0) the last two stages of the register 206 will contain ones and this will be detected by the AND gate 207. A binary one at the output of gate 207 ends the hunt mode and provides the nibble synchronization. When this occurs, the data is clocked out of the shift register (6 bits) into a data latch 235 and from there the data can be clocked into the processor and converted into 4 bit nibbles. Another circuit means is present to detect all zeroes in the shift register 206. When this occurs, the processor and shift register return to the hunt mode. The number loaded into register 1 83 provides a phase shift between the time at which transitions occur and the ideal time to shift data in and out of the register 206. This prevents the shifting of data during transitions.

Data which is to be transmitted is transferred into the data register 205. (Note only 6 bits representing a four bit nibble are transferred into the data register 205.) These 6 bits are then transferred into the shift register 206 and shifted out at the shift rate. As mentioned, if the packet being shifted out represents an acknowledgement, the shift rate corresponds to the rate of the incoming data. If the outgoing packet on the other hand is being sent to several cells, the shift rate is the nominal shift rate for the transmitting cell.

(Note that in Figure 23, data is shown leaving the register to only Pin A. For differential modes, the complement of Pin A is driven onto Pin B - and other variations are possible.)

G. I/O REGISTERS AND RESOURCE SHARING

Each I/O subsection has a number of registers which have bidirectional connections to the MBUS. These registers are in the I/O subsections 1 07, 1 08, 1 09 and 1 1 0 of Figure 1 2. The reading and writing of these registers under processor program control configures the I/O subsystems for proper operation. Figure 1 2 illustrates the four I/O subsections 1 07, 1 08, 1 09 and 1 1 0 and shows the connections to the low eight bits of the MBUS and the low six bits of ADBUS. Two ADBUS bits select one of the four I/O units and the remaining four bits are decoded to select one of the I/O control and status registers (described below) of that subsection. There are two lines from the PLA 1 36 of Figure 1 1 to control the action of the I/O subsections. One line is "Read" and the other line is "Write". When appropriate these lines are active on phase 3 of the clock cycles.

The I/O registers, functions and bit definitions are described below:

WRITE REGISTERS: (Controlled by the "Write" line). Event 0 Configuration Register:register, masking, 1 85 Figure Bit 0: Upon event Toggle pin A

Bit 1 Upon event Toggle pin B Bit 2 Upon event Latch 8 bit count Bit 3 Upon event close Ramp switch (momentary on) Bit 4: Upon event Load 8 bit counter

Bits5-7: Input Multiplexer: MUX 190, Figure 19.

000 Transition on pin A

001 Transition on pin B

010 Terminal Count event

011 Count Compare event 100 Ramp start event 101 Pin B compare event

Event 1 Configuration Register: masking register 186, Figure Bit 0: Upon event Toggle pin A Bit 1: Upon event Toggle pin B Bit 2: Upon event Latch 8 bit count Bit 3: Upon event close Ramp switch (momentary on) Bit 4: Upon event Load 8 bit counter Bits5-7: Input Multiplexer: MUX 191, Figure 19

000 Transition on pin A

001 Transition on pin B

010 Terminal Count event

011 Count Compare event 100 Ramp start event 101 Pin B compare event

I/O REGISTERS AND RESOURCE SHARING

8 Bit Counter Load Register: Counter load register 180; Figure 18

Bits 0-7 = count

Write Communications Data Out REgister: data register 205, Figure 23;

Bits 0-7 - data

Write Communications Configuration Register: (not shown) (loaded from MBUS)

Used to configure the communications subsystem for transmit and receive functions. Bit 0: 0 = Receive, 1 = Transmit Bit 1 : NOP Bit 2: NOP

Bit 3: Shift Register enable

Bit 4: Enter Hunt Mode

Bit 5: NOP Bit 6: NOP Bit 7: NOP

Output Configuration Register 0: (not shown) (loaded from M Used for setting analog and digital pin configurations. Bit 0: Enable pin A analog out Bit 1 : Enable pin A digital out Bit 2: Enable pin A pullup Bit 3: Enable pin A pulldown Bit 4: Enable pin B inversion Bit 5: Enable pin B digital out Bit 6: Enable pin B pullup Bit 7: Enable pin B pulldown

Output Configuration Register 1 : (now shown) (loaded from M Used for enable and compare functions.

Bit 0 Enable 8 bit counter Bit 1 Compare pin B to TTL reference

Bit 2 Compare pin B to adjustable D.C reference

Bit 3 Compare pin B to Ramp voltage

Bit 4 Compare pin B to pin A

Bit 5 Enable RS-485 driver Bit 6 Enable input hysteresis on pin A

Bit 7 Enable input hysteresis on pin B

Output Configuration Register 2: (not shown) (loaded from M Used for setting pin logic levels. Bit 0: Execute, load 8 bit counter with value in 8 bit

Counter Load Register Bit 1 Set pin A to logic level 1

Bit 2 Set pin A to logic level 0

Bit 3 Set pin B to logic level 1

Bit 4 Set pin B to logic level 0

Lower Half of Rate Multiplier Register: rate multiplier 1 78,

Figure 1 8 Lower byte of rate multiplier

Upper Half of Rate Multiplier Register: rate multiplier 1 78,

Figure 1 8 8 Bit Compare Load Register: compare load register 1 83,

Figure 1 8 Byte for comparison

READ REGISTERS: (controlled by "Read" line);

Read Event FIFO: FIFO 1 99, Figure 1 9 Bit 0: 0=Event 1 occurred 1=Event 0 occurred

Bit 1 : Pin A level during occurrence of event Bit 2: Pin B level during occurrence of event

Read l/O Condition Register: I/O Status:

Bit 0: Input pin A

Bit 1 : input pin B

Bit 2: 1 =ramp compare

Bit 3: NOP

Bit 4: NOP

Bit 5: 1 =F!FO I has data

0-FIFO empty

8 Bit Counter Latch: register 1 81 , Figure 1 8 Count Byte Communications Data Register: data latch 235, Figure 23 Data Byte

Communications Status Register: (not shown) (reads onto MBUS) Bit 0: Receive mode: 1 =data available in shift register

Transmit mode: 0=transmit latch ready Bit 1 : 1 =in Hunt Mode from Figure 23

RESOURCE SHARING: In the presently preferred embodiment there are five resources shared among the processors. They are the EEPROM and the four I/O subsections. A hardware "Semaphore Register" (SR) and five words in RAM are used in controlling resource sharing. Figure 30 illustrates how the multiprocessors share common resources. The SR 95 of Figure 1 2 reads and writes to bit 0 of the MBUS.

Each RAM word will contain one state: Idle, Proc.#1 , Proc.#2, Proc. #3 or Proc. #4. A processor may interrogate a RAM location before assignment of resource to see if a resource is busy. If the resource is not assigned it will then access the Semaphore Register as described below. (Alternately, a processor may, skip the initial RAM interrogation step and check the RAM location after it has accessed the Semaphore Register). If the resource already busy the processor must clear the Semaphore Register to "0" and wait to try again. If the resource is "Idle" the processor assigns a resource by changing the state of the RAM Register from "Idle" to "Proc.#x" and then clearing the Semaphore Register to "0". When the processor is finished with the resource, clears the RAM location to "Idle".

The SR is a one bit hardware register. During phase 3 of its respective cycle, if required, each processor may access the SR. In time sequence, this means that the processors may access the SR 295 once on one of four successive clock cycles (e.g., phases). The SR 295 is normally set to "0". In Figure 30, processors #1 and #3 are not requesting use of the SR 295 . Processor #2 is shown accessing the SR. If it receives a "0" at the beginning of the cycle it knows nothing is being currently assigned or cleared and it sets the appropriate RAM location and if it contains "Idle" the processor inserts its "Proc. # thus assigning the resource and then "clears" the SR to "0". If the process found that another processor was using the shared resource it does not assign its Proc. # and it then "clears" the SR to "0". In this event it must wait and try again.

Some operations such as those on the EEPROM may take many clock cycles so the processor should "assign" the RAM register but release the SR 295 while it is using the shared resource. When the processor is through with its operation using the assigned RAM location it accesses the SR again until it finds a "0". It then "clears" the RAM location to "idle" and "clears" the SR 295 to "0". Whenever a processor accesses the SR 295 and finds a "1 " it leaves the SR 295 in the "1 " state and must wait to try again. In the example in Figure 30 Processor #4 is shown as needing a shared resource. It interrogates the SR to find out if it is free. The processor uses a "test&set" operation and since the SR 295 was already "1 " the test & set operation leaves the register with a "1 ". It must now wait and try again. It will keep trying until it gets access to the SR 295 and it finds the resource in the RAM word is "idle".

V. PROTOCOL A. CONTENTION IN GENERAL

In a typical application the communications network among the cells is lightly loaded and the cells will experience little or no contention delay. In the case of heavy traffic, the network can saturate. A heavy load will generate collisions and hence require retransmissions. If retransmissions continue to collide, the network can possibly saturate. The contention backoff algorithm used in the network quickly spreads the traffic over a longer time period so that the system can recover from saturation. If the traffic is not spread over a long time period, the system will be unstable; it will not recover from saturation.

Access to a subchannel under contention conditions is regulated by two mechanisms, deferring and backing off. Deferring is a collision avoidance technique used in group acknowledgements. Backing off is a traffic or load leveling technique. Deferring consists of counting free slots. When the number of free slots that the cell has seen equals the defer count, the cell transmits its packet in the next available slot.

When backing off, the cell increases its waiting time before attempting to retransmit a packet that has suffered a collision. The amount of this increase is a function of the number of collisions or retransmissions. The algorithm implementing this function is called the backoff or contention algorithm.

The network uses a carrier sense multiple access method of resolving contention for the communications channel. When a cell is ready to transmit it first listens to the communications channel. If it hears another cell transmitting, it waits for a clear channel. Once it detects a clear channel, a cell may delay before transmitting. The method of determining that delay is determined by the contention algorithm.

Time on the channel is measured in slots, each slot being M bits at the most recently detected receive baud rate (i.e., shift rate). When a cell delays before transmitting, it waits an integral number of slots. When a cell detects a clear channel, it may delay and then when it is ready to transmit, it attempts to transmit on a slot boundary. If a cell is transmitting a packet that has suffered a collision, it delays a time period determined by the backoff algorithm. Backoff delay is randomized uniformly over N slots, N is adjusted by the backoff algorithm. Its smallest value is 2 and it is adjusted upward by the backoff algorithm before each retransmission of a packet. Its maximum value is 2¹⁰.

B. GROUP ACKNOWLEGEMENT PACKET CONTENTION

A packet from a group announcer to a set of group listeners will cause each of those listeners to send an acknowledgement to the announcer. Without a method of arbitrating contention among those acknowledgements, they will always collide. To avoid this problem, a built in reservation system for group acknowledgements is used. A listener cell uses its group member number to determine which slot to use for its acknowledgement. Group member 5 will transmit its acknowledgement in the 5th free slot following reception of the original packet. The result is that group member 1 will transmit its acknowledgement in the first slot following the original packet. Group member two will transmit its acknowledgement in the first slot following first group member's acknowledgement. This process continues until the last group member has replied to the original packet. If a group member does not reply and thus leaves its reply slot empty, the next group member replies in the next slot.

The contention and I/O state diagram is shown in Figure 24. The following table sets forth the states and their descriptions.

Contention States

State Name Description 0 Idle Time the slot boundaries while looking for receive data transition 1 Bit Sync Establish baud rate synchronization with received signal.

2 Byte Sync Wait for the start of packet flag.

3 Rev Receive the packet.

4 IPG Delay Inter Packet Gap Delay. Delay for n bit times after the end of the l packet on the subchannel (whether this neuron transmitted it or received it).

5. Backoff Wait M slots where M was set by the last execution of the Delay backoff algorithm or by the ARQ protocol software.

6. Xmt Transmit a packet in the next slot.

7. Jam Transmit a jam pattern (all ones) for the jam period (specified in bit times). Execute the backoff algorithm to set the backoff slot count.

Contention State Transitions

State Event Action Next State 0. Idle A. Transitions Detected none 1. Bit Sync 0. Idle L. Packet to Xmt none 5. Backoff Delay 1 . Bit Sync B. Sync Achieved none 2. Byte Sync 1 . Bit Sync G. No Transitions none 4. IPG Delay Byte Sync

2. Byte Sync F. Hunt Timeout none 1 . Bit Sync 2. Byte Sync C. Starting Flag none 3. Rev Detected

3. Rev E. Abort Detected none 1. Bit Sync 3. Rev D. Ending Flag Set Pckt Rcvd Flag 4. IPG Delay 3. Rev N. Packet Too Long none 1 . Bit Sync

4. IPG Delay M. Delay Done none 0. Idle

5. Backoff J. Delay Done none 6. Xmt Delay

5. Backoff A. Transitions Detected none 1 . Bit Sync Delay

6. Xmt I. Collision Detected Calculate Backoff

Delay 7. Jam δ. Xmt H. Xmt Done none 0. Idle

7. Jam K. Jam Done none 5. Backoff Delay

C. COLLISION DETECTION In the currently implemented embodiment collision detection is not used. Ordinary circuits can be used to provide this feature with the cells providing responses as set forth in IEEE802.3. Upon detecting a collision, the cell can transmit a jamming signal for one slot time to make sure that all cells on the channel detect the collision. It then ceases transmitting and executes the backoff algorithm. The backoff algorithm adjusts the contention randomization interval. IEEE802.3 uses the number of collisions experienced by the packet to calculate the backoff interval. The cell network may not always have collision detection so the cell's backoff algorithm may use the protocol's inferred collision to calculate the backoff interval. If the cell has collision detection, it detects a collision in the same slot in which it occurs and retries the transmission (after the backoff interval).

For cells without collision detection where a collision occurs, the cell discovers it when the protocol timeout period expires. If a ceil is sending a packet to multiple destinations (the normal case), it infers a collision if at the end of the protocol timeout period, no replies have been received from any of the destinations. If even one reply is received, there was no collision at the transmit point and the retransmission takes place without an increased delay due to backoff. The cell then executes the backoff algorithm just as it does with collision detection, using the inferred collision count. After the backoff interval, the cell transmits the packet.

Therefore, the difference between collision detection and collision inference is in the length of time it takes the cell to discover that a collision has occurred.

D. BACKOFF ALGORITHM The backoff algorithm used in the currently preferred embodiment is set forth in IEEE802.3 standard, a truncated binary exponential backoff. The backoff interval is an exponential function of the number of collisions (detailed or inferred) since the last successful transmission. An exponential backoff algorithm gives the system the stability it needs to recover from saturation conditions. By exponentially spreading out the load in a saturated system, the algorithm allows the system to recover. Backoff interval in slots - R such that R - random number linearly distributed over the interval: 0 <R<2 EXP [min (1 0, n)]

where n = number of collisions. When a cell has two transceivers attached, it transmits every packet via both transceivers. Since the transceivers access different subchannels, they will experience different load conditions. Each transceiver is treated as a separate subchannel and has its own backoff parameters (collision count and backoff interval). The backoff parameters are "kept" by the cells, one set for each transmission. The random number for the backoff algorithm is generated by one of two methods: 1. by a pseudorandom number generation algorithm seeded with the 48 bit cell ID (guaranteed to be unique as discussed), 2. by running a counter and saving the low order bits when an external event is detected. The slots are equal in durations to bit rate of the last received data. Note: if each cell used its internal bit rate, slot durations would vary from cell-to-cell.

E. CONTENTION TIMER Packets that have multiple routes to a destination may experience a long contention delay via one route and a shorter delay while traveling simultaneously via another route. If that contention delay is allowed to be too long, the later packet could arrive after the destination's receive sequence number has cycled back to the same sequence number in the packet. A packet could thus arrive out of sequence without the ARQ protocol detecting it. To prevent this type of error, each packet uses the contention timer field (Figure 6) that is decremented by the number of slots that the packet has waited for contention at each hop in a multihop route. When the count reaches zero, the packet is discarded.

F. ARQ PROTOCOL The cell uses a sliding window protocol with a window size of 1 and modulo 2 sequence numbering (equivalent to a stop and wait protocol). The link control mechanism is very similar to the HDLC asynchronous balanced mode. The principal difference being that with 1 bit sequence numbering instead of acknowledging packets with the poll/final bit set, every information packet must have an acknowledgement.

Before the ARQ mechanism can work, a connection must be established between the two communicating devices (cell or network control devices). The connection process is described in the "connection" section later in this application. The ARQ mechanism only operates when the cell is in the connect state. The ARQ states may be considered as substates of the connect state.

When a cell transmits a message, it waits for a reply from the destination. If the cell does not receive an acknowledgement within a predefined time out period, it assumes that the message was lost and it transmits the message again. Two types of packet may be used to carry an acknowledgement, an acknowledgement-only packet or an information packet. The acknowledgement is carried in the receive sequence number of the packet. The acknowledgement- only packet has no message field and is identified by the ACK command in the link command field. An information packet does contain a message field and is identified by the INFO command in the link command field.

Figure 25 is the link level ARQ state diagram and along with the following table, defines the various ARQ states.

A cell must store a transmit sequence number for each addressee with whom it communicates. An addressee can be a cell, a group, or a control device. For receiving, a cell must save the receive sequence number of each source from which it receives. A source can be a cell, a group, or a control device. When a cell receives a message, it checks the CRC on the message. If the CRC is not valid, the cell does not reply to the message. The cell receiving a message also checks the message's sequence number. If the sequence number indicates that this is a duplicate packet, the cell acknowledges the receipt of the packet to the sender but does not pass the packet to the application software. The ARQ protocol uses a bit that means "this is a retransmission by the sender". A receiver will not acknowledge a duplicate message unless the message has its retransmit bit on. The cell saves the sequence number for the last received message for each group for which it is a listener. It has a separate 1 bit transmit sequence number and 1 bit receive sequence number for messages addressed with the cell address (used when communicating with control devices).

Cell to cell communications is via group addresses. Direct addressing with cell addresses is used for network control functions. The cell will be communicating with a grouping device or network controller in those cases. A cell can have only one conversation at a given time that uses cell addresses because it has provisions to store only one set of those sequence numbers.

When a control device wishes to communicate with a cell, it opens communications by sending a packet with a connect command in the link control field. That command initializes the sequence numbers. After receipt of that command, the cell will not accept messages addressed to it (via cell address) by another control device until the conversation ends. The conversation ends when the control device sends the cell a disconnect command.

The period of time that the cell waits for an acknowledgement of a message depends on the type of routing used. In general, the cell allows enough time for the packet to arrive at its destination, plus protocol processing time in the destination cell and the transit time for the return packet carrying the acknowledgement.

The protocol timeout period for multihop packets is also influenced by the collision count. Even in very noisy environments, it is more likely that the reason a packet failed to reach its destination in time is due to a contention rather than a transmission error. When a packet is retried, it is assumed that the collision count is an indication of system load and the expected contention delay for a multihop packet. The delay period for multihop packets is adjusted upward as a function of collision count. The timeout period is therefore a function of the transmission baud rate, the number of hops and the collision count.

G. LINK CONTROL COMMANDS Link control commands control the operation of the ARQ protocol and the link connection process (see next section). The link command field of a packet always contains a link command. ARQ Protocol Commands

INFO Information Packet (requires acknowledgement)

ACK Acknowledgement Only Packet (does not require acknowledgement) Connection Control Commands

CONN Connect

DISC Disconnect

SI Set Initialization XND Exchange Network Data

Replies to Connection Control Commands

CMDR Command reject RD Request Disconnect

RI Request Initialization

UA Unnumbered Acknowledge Only packets with the ACK and INFO commands use sequence numbering. The INFO packets have two sequence numbers, a transmit sequence number and the sequence number of the last packet received. ACK packets have both sequence number fields but the transmit sequence number is ignored by the destination.

Packets with commands other than ACK or INFO are called unnumbered packets. Unnumbered packets are acknowledged in a stop and wait fashion via a UA command. Unnumbered packets do not contain a message field.

H. CONNECTION CONTROL Before a control device can communicate with a cell, it must establish a connection with the cell. Establishing a connection consists of initializing the sequence numbers and putting the control device and cell into a known state. The connection establishment and maintenance procedures are governed by state machines implemented in software. An announcer cell must establish a connection with each listener cell in its group. Only when the connections have been established may the announcer communicate with the listeners. Connections are controlled by a subset of the link control commands. Commands are issued by a primary station. A secondary station receives a command and sends a reply to the primary. In a group, the primary station is the announcer. The listeners are secondaries. When a network control device communicates with a cell, the control device is the primary, the cell is the secondary. The link control commands and their responses are shown below. The INFO and ACK commands are ARQ protocol commands; the rest are connection control commands.

S I Set Initialization

CMDR Command reject: Sent only by secondary in Connect State. Retry SI. UA Unnumbered ACK.

XND Exchange ID & Network data: This command is sent only in when the primary is in the disconnect state.

XND Exchange ID & Network data: The secondary send an XND response only if it is in the disconnect state. If it receives an XND while in any other state, the secondary responds with CMDR.

CMDR Command reject: sent only by secondary in connect state. Disconnect secondary; then try XND again.

The connection state diagrams of Figures 26 and 27 refer to primary and secondary stations. The primary station controls the connection. The secondary can request that the state of the connection change but the secondary cannot change the connection unless commanded to do so by the primary station.

NOTE: Retries: A reply may be retried N times. The event that causes retry N+1 is defined to be a fatal error and causes initialization. The cell maintains one retry count and it is incremented when any reply other than INFO or ACK is retried. The retry count is cleared whenever a non-retry reply is sent to the primary cell.

I. ABORT SEQUENCE

A cell transmitting a packet can abort the packet by transmitting an abort sequence instead of .continuing to transmit the packet. The Abort sequence is a group of at least 1 2 ones transmitted in succession. A receiving cell identifies an abort from the code verifier of Figure 1 6. A receiving packet treats any 3 of 6 code violation as an abort. One result of this is that a link idle condition results in an abort. If the link is idle (no transitions) for more than a bit time, the result is a code violation. When a cell receiving a packet detects an abort sequence, it discards the portion of the packet that it has clocked in and begins searching for a new packet preamble. The abort sequence is also used for jamming after a collision is detected.

J. SYSTEM ID Referring to Figure 29, themethod by which the 48 bit system ID is used within the packets is illustrated. Thirty-two bits of the system ID shown as field 251 is placed directly into the packet as indicated by the field 255. The remaining 1 6 bits are used in the calculation of the packet CRC. Initially, the CRC register begins with all ones as indicated by the field 252 at the start of the CRC calculation. Then the 1 6 bit field 250 of the system ID is used in the CRC calculation to provide a^' 1 6 bit field 253. The field 253 is stored in the EEPROM and used as a preset CRC field ea ch time a packet CRC is calculated. When a packet is to be transmitted once the preset field is stored, the stored CRC field is coupled to the CRC register. The 1 6 bit packet CRC field is calculated using this present field and hte other fields in the packet used to calculate the packet CRC. (All fields except the contention timer field are used.) The other 32 bits of the system ID are transmitted within the packet.

When a packet is received, the processor calculates a CRC for the received packet by first placing its stored CRC preset field in its CRC register and then computing the packet CRC (again, the contention timer field is not used). If the newly computed CRC field does not match the field in the packet, it is assumed that the packet has been improperly transmitted or that the transmitted packet, if correct received, has a different system ID and thus should be discarded. VI. GROUPING DEVICE

The grouping device can take various forms and can be realized with commercially available hardware such as a personal computer. These computers can be readily programmed to perform the various functions described in the application performed by the grouping device. For example, they can be readily programmed to provide the packets needed to communicate with the cells for grouping. Other functions such as the generation of the random number used within the packets can be generated with well-known programs.

An Apple II computer, for instance, may be used as a grouping device. The 48 bit system ID may be stored on a disk; or, a printed circuit card may be provided which engages one of the slots of the Apple II computer, the card can contain the system ID which is taken from a cell such as cell 232 of Figure 28. As groups are formed, the assigned group numbers, member numbers, etc., can be stored on the disk or stored in an EEPROM on a card. In Figure 28, the elements of a presently preferred grouping device are illustrated. They include a CPU 226 which may be an ordinary microprocessor. The CPU communicates with a memory which may comprise a RAM 227, ROM 228 and storage means 229 for storing the system ID. Where a floppy disk is used the system ID and program (otherwise stored in ROM 228 ) are stored on the disk, with the program being transferred to RAM for execution.

A display means 230 such as a ordinary monitor is coupled to the CPU to provide a display to the user, for instance, the display can be used to provide lists of the groups with their ASCII names. A keyboard 231 is used to allow commands to be entered into the CPU. The CPU is shown coupled to a cell 232 with the cell being coupled to a network through transceiver 233. The cell 232 is part of the grouping devices and the cell's ID is used by the grouping devices as a system ID. Typical messages transmitted by the computer to the cell are shown in Appendix B, for example, the message of assigning the destination cell to be an announcer in a designated group is a message generated by the grouping device. The grouping device can communicate directly with the cell over one of the three pairs of leads which are coupled to the I/O subsections or through the select pin which allows messages from the CPU 226 to be read to the fourth I/O subsection.

Thus, a network for sensing, communicating and controlling which has distributed intelligence has been described. While in this application a simple example of use of cells in a home environment has been described, it will be obvious to one skilled in the art that the disclosed invention may be used in numerous other applications. Appendix C to this application contains a list of some other applications in which the present invention may be used. Appendix A, Packet Examples

Routing Types for Packet Examples 1 Fully Addressed

2 Open Flooding

3 Restricted Flooding

4 Group Flooding

NOTE: The packet sizes are in cell memory bits (before 3-of-6 encoding). A packet on a communications subchannel, after conversion to 3 of 6 code, is 50% larger.

Single Hop

Packet Format: Preamble, 1 6 bits Flag, 4 bits

Destination cell Address, 48 bits Contention Timer, 1 0 bits Contention Timer Checksum, 6 bits Hop Count, 4 bits Randomizer, 8 bits Link Control Retransmit Flag, 1 bit Rev Seq, 1 bit Xmt Seq, 1 bits Unused, 1 bit Command, 4 bits Network Control

Routing Type, 4 bits = 1 (Fully Addressed) Source Cell Address, 48 bits Message, 1 6 to 51 2 bits Message Type, 8 bits Message Contents, 8 to 51 1 bits Encryption Check, 1 6 bits CRC, 1 6 bits Flag, 4 bits Single Hop

Reply Format: Preamble, 1 6 bits Flag, 4 bits System ID, 32 bits Destination Cell Address, 48 bits Contention Timer, 1 0 bits Contention Timer Checksum, 6 bits Hop Count, 4 bits Randomizer, 8 bits Link Control Retransmit Flag, 1 bit Rev Seq, 1 bit Xmt Seq, 1 bits Unused, 1 bit Command, 4 bits Network Control

Routing Type, 4 bits = 1 (Fully Addressed) Source Cell Address, 48 bits Encryption Check, 1 6 bits CRC, 1 6 bits Flag, 4 bits

Multihop Full Address

Packet Format: Preamble, 1 6 bits Flag, 4 bits System ID, 32 bits Next Cell Address, 48 bits Contention Timer, 1 0 bits Contention Timer Checksum, 6 bits Hop Count, 4 bits Randomizer, 8 bits Link Control Retransmit Flag, 1 bit Rev Seq, 1 bit Xmt Seq, 1 bits Unused, 1 bit Command, 4 bits Network Control

Routing Type, 4 bits = 1 (Fully Addressed) Cell Address List

Address Count, 4 bits

Addresses, 48 - 768 bits Source Cell Address, 48 bits Message, 1 6 to 51 2 bits Message Type, 8 bits Message Contents, 8 to 51 1 bits Encryption Check, 1 6 bits CRC, 1 6 bits Flag, 4 bits

Multihop Full Address

Routing Type, 4 bits = 1 (Fully Addressed) Cell Address List

Address Count, 4 bits

Addresses, 48 - 768 bits Source Cell Address, 48 bits Encryption Check, 1 6 bits CRC, 1 6 bits Flag, 4 bits

Open Flooding

Packet Format: Preamble, 1 6 bits Flag, 4 bits System ID, 32 bits

Broadcast Address, 48 bits = All Zeros Contention Timer, 1 0 bits Contention Timer Checksum, 6 bits Hop Count, 4 bits Randomizer, 8 bits Link Control Retransmit Flag, 1 bit Rev Seq, 1 bit Xmt Seq, 1 bits Unused, 1 bit Command, 4 bits Network Control

Routing Type, 4 bits = 2 (Open Flooding) Destination Cell Address, 48 bits Source Cell Address, 48 bits Message, 1 6 to 51 2 bits Message Type, 8 bits Message Contents, 8 to 51 1 bits Encryption Check, 1 6 bits CRC, 32 bits Flag, 4 bits

Open Flooding

Reply Format: Preamble, 1 6 bits Flag, 4 bits System ID, 32 bits

Routing Type, 4 bits = 2 (Open Flooding) Destination Cell Address, 48 bits Source Cell Address, 48 bits Encryption Check, 1 6 bits CRC, 1 6 bits Flag, 4 bits

Restricted Flooding

Packet Format: Preamble, 1 6 bits Flag, 4 bits System ID, 32 bits

Routing Type, 4 bits = 3 (Restricted Flooding) Destination Cell Address, 48 bits Source Cell Address, 48 bits Message, 1 6 to 51 2 bits Message Type, 8 bits Message Contents, 8 to 51 1 bits Encryption Check, 1 6 bits CRC, 1 6 bits Flag, 4 bits

Restricted Flooding

Reply Format: Preamble, 1 6 bits Flag, 4 bits System ID, 32 bits

Routing Type, 4 bits = 3 (Restricted Flooding) Destination Cell Address, 48 bits Source Cell Address, 48 bits Encryption Check, 1 6 bits CRC, 1 6 bits Flag, 4 bits

Group Announcement

Packet Format: Preamble, 1 6 bits Flag, 4 bits System ID, 32 bits Group Address, 48 bits Contention Timer, 1 0 bits Contention Timer Checksum, 6 bits Hop Count, 4 bits Randomizer, 8 bits Link Control Retransmit Flag, 1 bit Rev Seq, 1 bit Xmt Seq, 1 bits Unused, 1 bit Command, 4 bits Network Control

Routing Type, 4 bits = 4 (Group Flooding) Source Member Number, 8 bits Destination Member Number, 8 bits, (0 = broadcast) Message, 1 6 to 51 2 bits Message Type, 8 bits Message Contents, 8 to 51 1 bits Encryption Check, 1 6 bits CRC, 1 6 bits Flag, 4 bits

Group Announcement

Reply Format: Preamble, 1 6 bits Flag, 4 bits System ID, 32 bits Group Address, 48 bits Contention Timer, 1 0 bits Contention Timer Checksum, 6 bits Hop Count, 4 bits Randomizer, 8 bits Link Control Retransmit Flag, 1 bit Rev Seq, 1 bit Xmt Seq, 1 bits Unused, 1 bit Command, 4 bits Network Control

Routing Type, 4 bits = 4 (Group Flooding) Source Member Number, 8 bits Destination Member Number, 8 bits Encryption Check, 1 6 bits CRC, 1 6 bits Flag, 4 bits

Probe

Packet Format: Preamble, 1 6 bits Flag, 4 bits System ID, 32 bits

Routing Type, 4 bits = 3 (Restricted Flooding) Destination Cell Address, 48 bits Source Cell Address, 48 bits Message, 49 to 769 bits Message Type, 8 bits

Message Contents, 48 to 768 bits (Route List) Encryption Check, 1 6 bits CRC, 1 6 bits Flag, 4 bits

Probe

Reply Format:

Preamble, 1 6 bits

Flag, 4 bits

System ID, 32 bits

Broadcast Address, 48 bits = All Zeros

Contention Timer, 1 0 bits

Contention Timer Checksum, 6 bits

Hop Count, 4 bits

Randomizer, 8 bits

Link Control

Retransmit Flag, 1 bit

Rev Seq, 1 bit

Xmt Seq, 1 bits

Unused, 1 bit

Command, 4 bits

Network Control

Routing Type, 4 bits = 3 (Restricted Flooding)

Destination Cell Address, 48 bits

Source Cell Address, 48 bits

Message Field,

Message Type 8 bits Message contents, Route List

Encryption Check, 1 6 bits

CRC, 1 6 bits

Flag, 4 bits

Broadcast Command

Packet Format: Preamble, 1 6 bits Flag, 4 bits System ID, 32 bits

Broadcast Address, 48 bits = All Zeros Contention Timer, 1 0 bits Contention Timer Checksum, 6 bits Hop Count, 4 bits Randomizer, 8 bits Link Control Retransmit Flag, 1 bit Rev Seq, 1 bit Xmt Seq, 1 bits Unused, 1 bit Command, 4 bits Network Control Routing Type, 4 bits = 3 (Restricted Flooding) or 2 (Open Flooding) Source Address, 48 bits Message, 1 6 to 51 2 bits Message Type, 8 bits Message Contents, 8 to 51 1 bits Encryption Check, 1 6 bits CRC, 1 6 bits Flag, 4 bits

Broadcast Command

Reply Format: NO REPLY

Appendix B - Message Types

Probe

Function: Determine the best route from the announcer to the listener.

Source: Group Announcer

Address Type: Cell

Routing Method: Restricted Flooding

Message Type: 2 (Number for 3 bit field)

Message Content: Address Count (1 byte), (number of cell IDs in probe packet - this is the number of cells rebroadcasted packet)

Address List

Probe Result

Function: report the address list in the first probe packet received by the destination Cell.

Source: Cell previously addressed by a Probe message.

Address Type: Cell

Routing Method: Restricted Flooding

Message Type: 3

Message Content: Address Count (1 byte), Address List

Assign Group Announcer

Function: Assign the destination Cell to be an announcer in the designated group.

Source: Grouping Device

Destination: Cell

Address Type: Cell or Group Member

Routing Method: Restricted Flooding or Group Flooding

Message Type: 4

Message Content: Group Number, Member Number

Deassign Group Announcer

Function: Deassign the destination Cell from serving as an announcer in the designated group.

Source: Grouping Device Destination: Announcer Cell

Address Type: Cell or Group Member

Routing Method: Restricted Flooding or Group Flooding

Message Type: 5

Message Content: none

Assign Group Listener

Function: Assign the destination Cell to be a listener in the destinated group.

Source: Grouping Device

Destination: Cell

Address Type: Cell or Group Member

Routing Method: Restricted Flooding or Group Flooding

Message Type: 6

Message Content: Group Number, Member Number

Deassign Group Listener

Function: Deassign the destination Cell from serving as a listener in the designated group.

Source: Grouping Device

Destination: Listener Cell

Address Type: Cell or Group Member

Routing Method: Restricted Flooding or Group Flooding

Message Type: 7

Message Content: none

Assign Group Repeater

Function: Assign the destination Cell to be a repeater in the designated group.

Source: Grouping Device

Destination: Cell

Address Type: Cell or Group Member

Routing Method: Restricted Flooding or Group Flooding

Message Type: 8

Message Content: Group Number, Member Number

Deassign Group Repeater

Function: Deassign the destination Cell from serving as a repeater in the designated group.

Source: Grouping Device

Destination: Group Repeater Cell

Address Type: Cell or Group Member

Routing Method: Restricted Flooding or Group Flooding Message Type: 9 Message Content: none

Assign Repeater

Function: Assign a Cell to act as a repeater. Used to assign Cells that are not normally allowed to be a repeater, i.e. a Cell with one transceiver on a nonradiated medium.

Source: Control device

Destination: Cell

Address Type: Cell Routing Method: Fully Addressed, Open Flooding, Restricted Flooding

Message Type: 1 0

Message Content: none

Shutup

Function: Broadcast message telling all Cells to stop transmitting until commanded to resume.

Source: Control Device

Destination: Cells

Address Type: Broadcast or Cell

Routing Method: Restricted Flooding or Open Flooding

Message Type: 1 1

Message Content: none

Report your Input

Function: Command a Cell to report its input.

Source: Cell or Control Device

Destination: Cell

Address Type: Any

Routing Method: Any

Message Type: 12

Message Content: Input number (byte).

Report your Output

Function: Command a Cell to report its output.

Source: Control Device or Cell

Destination: Cell

Address Type: Any

Routing Method: Any

Message Type: 13

Message Content: Output number (byte).

Download Function: Download data or code

Source: Control Device

Destination: Cell

Address Type: Any

Routing Method: Any

Message Type: 14

Message Content: Address, length, code

Set communciation parameter

Function: Set a Communication Parameter in the Cell

Source: Control Device

Destination: Cell

Address Type: Any

Routing Method: Any

Message Type: 1 5

Message Content: Parameter number, value

Announcement

Function: Announce Sensor Data

Source: Group Announcer

Destination: Group

Address Type: Group, Broadcast

Routing Method: Group Flooding

Message Type: 1 6

Message Content: 0 - 255 (one byte)

APPENDIX C APPLICATIONS

CATEGORY SUBCATEGORY APPLICATION

General Sensing Functions

Usage Communication Functions

Control Functions

Agriculture Crop Management Crop Sensor/Comm Irrigation Ctrl/Comm Land Leveler Sensor Comm Pest Sensor/Comm (with cell IDs identifying animals)

Livestock Detector/Tracker

Feed Sense/Ctrl/Comm

Milker Sense/Ctrl/Comm

Weight Sensor/Comm

Herder Signal Device

Commercial Banking ATM Card

Electronic Money

Commercial Cash Register Sense/Ctrl/Comm

Elevator Sense/Ctrl/Comm

Slot Machine Sense/Ctrl/Comm

Vending Machine Sense/Ctrl/Comm

Commercial, Misc Diaper Sensor/Comm Pager Ctrl/Comm Protechnics, Sensor Ctrl Stamp I.D. Watch Ctrl/

Construction Decay Sensor/Comm Post Sensor/Comm

Energy Management Sensor Sense/Comm Thermostat Ctrl/Comm Utility Sensor/Comm Vent Ctrl/Comm

Security Lock Sense/Ctrl/Comm

Smart Keys (Serial #)

Communication Communications Cable Elimination

Channel Ctrl/Comm

Network Configuration Ctrl/Comm

Cell to Anything Bridge

Phone I.D. (Cell I.D.)

Phone to Cell Bridge Telemetry Ctrl/Comm Wiring Elimination

Computer Slow Data Network

Network Architecture Artificial Intelligence Configuration Ctrl Copy Protection Parallel Processing Nodes

Peripheral Cable Elimination

Keyboard Sense/Comm Mouse Sense/Comm Wiring Elimination

Develop. System Emulator Device Consumer Appliances Sensor Sense/Comm Switch Sense/Ctrl/Comm

Consumer, Misc Detector/Tracker (Electronic Serial #)

Low Battery Detector Smart Lottery Ticket Entertainment Amusement Park Ctrl'r

Arcade Game Ctrl'r Cable TV Access Ctrl'r Cable TV Sample Ctrl'r CD Player Ctrl'r Special Effects Ctrl'r

Stereo Ctrl'r TV Ctrl'r VCR Ctrl'r

Home Improvement Central Clock Sys Curtain Ctrl/Comm Door Sense/Comm

Garage Door Ctrl'r

Intercom

Intercom Ctrl'r

Pool Ctrl'r Sense/Ctrl/Comm

Smoke/Fire Detector Window Sense/Ctrl/Comm

Pets Detector/Tracker (Electronic Serial #)

Pet Ctrl/Trainer

Education Education, Misc Interactive Book Sense/Ctrl/Comm Test Sense/Comm

Engineering Data Acquisition DAC/ADC Instrumentation DAC/ADC

Switch Sense/Ctrl/Comm

Home Electrical Light Ctrl/Comm

Recepticle Sense/Comm/Ctrl Switch Sense/Ctrl/Comm All forms of sensing All forms of control

Home Improvement Central Clock Sys Curtain Ctrl/Comm Door Sense/Comm

Garage Door Ctrl'r

Intercom

Intercom Ctrl'r

Pool Ctrl'r Sense/Ctrl/Comm

Smoke/Fire Detector Window Sense/Ctrl/Comm

Security Lock Sense/Ctrl/Comm

Smart Keys (Serial #)

Vibration/Motion Sense/Comm window Sense/Ctrl/Comm

Sprinkler Sys Timer Ctrl/Comm Valve Ctrl/Comm Wetness Sense/Ctrl

Industria l Energy Management Sensor Sense/Comm Thermostat Ctrl/Comm Utility Sensor/Comm Vent Ctrl/Comm

Industrial Equipment Oil Drill Sensor/Ctrl/Comm

Power Load Sense/Ctrl/Comm

Utility Sensor/Comm

Security Lock Sense/Ctrl/Comm

Smart Keys (Serial #)

Vibration/Motion Sense/Comm Window Sense/Ctrl/Comm

Security , industrial Copy Protection

Detector/Tracker (Electronic Serial #)

Personnel Badge I.D.

Law Security, Law Copy Protection I.D. Card (Serial #) Gun I.D.

Passport (Serial #) Shoplifter Detector

Manufacturing CIM Artificial Intelligence Wiring Elimination Production Ctrl Detector/Tracker (Electronic Serial #)

Inventory Sense/Comm

Process Ctrl Line Balance Production Automation Production Flow/Sense

Robotics Detector/Tracker (Electronic Serial #)

Robot Sense/Ctrl/Comm

Medical Medical, Misc Bio-Feedback Bionics

Handicapped Interfaces

Heart Pacer

Implants

Medical Alert Sense/Comm

Medicine Alert Sense/Comm

Patient Monitoring

Personal Dispenser Ctrl/Comm

Personal Monitors

Prosthetics

Military Military, Misc Copy Protection

Damage Ctrl Sense/Comm

Detector/Tracker (Electronic Serial #)

Personnel Badge I.D. Redundant Comm SDI Sense/Ctrl/Comm Sonna Buoy Sense/Comm Spying Sense/Ctrl/Comm Position Sense/Ctrl/Comm

System Diagnostics Sense/Comm War Game Monitor/Sim Weapon Sense/Ctrl/Comm

Security Lock Sense/Ctrl/Comm

Smart Keys (Serial #)

Vibration/Motion Sense/Comm Window Sense/Ctrl/Comm

Scientific Weather/Earthquake/etc. sensor Transportation Automotive General sensing General communication General control Anti-lock Breaking Sys

Complex Cable Elimination

Gauge Ctrl

In Dash Map/Locator Instrument Panel Ctrl License Plate I.D. & Comm

Light Ctrl/Comm Regulator Sense/Comm Smart Keys (Serial #)

Switch Sense/Ctrl/Comm System Diagnostics Sense/Comm Wiring Elimination

Avionics Anti-lock Breaking Sys

Complex Cable Elimination

Gauge Ctrl

Instrument Panel Ctrl Light Ctrl/Comm

Regulator Sense/Comm

Sensor Sense/Comm Switch Sense/Ctrl/Comm System Diagnostics Sense/Comm Wiring Elimination

Transportation, Misc Emergency Locator (ELT) Sense/Comm

Traffic Monitor/Ctrl

Traffic Signal Sense/Ctrl/Comm

Tpy/Hobby/Spo Game 3-D "Chip-Wits" Sense/Ctrl/Comm

Bingo Card Sense/Comm Game sense/Ctrl/Comm

Hobby Camera Sense/Ctrl/Comm

Hobby Kit Sense/Ctrl/Comm

Magic Equipment Sense/Ctrl/Comm

Miniature Train Ctrl/Comm Remote Ctrl Sense/Ctrl/Comm

Sport Emergency Locator (ELT) Sense/Comm Trap Line Sensor

Sport Accessory Sense/Ctrl/Comm

Toy Lego-Bot Sense/Ctrl/Comm

Media Interactive Toy Sense/Ctrl/Comm

Animated Toy Sense/Ctrl/Comm

Claims

1 . In a network for sensing, communicating and controlling having a plurality of ceils each of said cells comprising: processing means for preparing packets, each of said packets having a predetermined number of protocol fields including a source address field and a destination field; said processing means for preparing predetermined messages for carrying out at least one of said sensing, communicating and controlling, said messages being included in said packets; said processing means generating a random number of a predetermined length, said random number being included in a field within said packet; interface means for interfacing between said processing means and said network for communicating packets to and from said network whereby a cell is realized.

2. The cells defined by Claim 1 wherein said packets of one of said ceils are directed to a group of said cells and said destination field of said one cell contains a number representative of the number of cells in said group being addressed by said packets, and, said destination field also including member numbers for each of said cells being addressed.

3. The cells defined by Claim 1 wherein said source address field contains a unique identification number of the one of said cells preparing said packet.

4. The cells defined by Claim 3 wherein said destination field of said packets contains a unique identification number of the one of said cells which is designated to receive said packets

5. The cells defined by Claims 1 or 4 wherein said packets made up of segments of six bit codes each segment containing three binary ones and three binary zeroes.

6. In a network for sensing, controlling and communicating which network has a plurality of cells a method for communicating a packet from a first of said ceils to a second of said cells where said packet is repeated by others of said cells (repeater cells) before arriving at said second cell comprising the steps of: generating a random number with said first cell and including said random number in a field in said packet; performing a calculation by said repeater cells on predetermined fields in said packet which fields include said random number field to generate a first number, storing said first number by said repeater cells; performing said calculation on subsequent packets received by repeater cells to provide a second number; comparing said second number to said first number; rebroadcasting said subsequently received packet if said second number is different than said first number; whereby rebroadcasting of said packet more than once by said repeater cells is limited.

7. The method defined by Claim 6 wherein said storing step comprises storing said number in a circular list.

8. The method defined by Claims 6 or 7 wherein said calculation performed by said repeater cells comprises the computation of a cyclic redundancy code.

9. The method defined by Claim 8 including the step of converting said packet into segments of six bit codes where each segment contains three binary ones and three binary zeroes.

1 0. In a network for sensing, communicating and controlling where packets are communicated between a plurality of cells, an improved method for including in said packets a system identification number of N bits comprising the steps of: including a portion of said N bit identification number in a field within each of said packets; using the remaining bits of said N bit identification number in the calculation of a cyclic redundancy code (CRC), said CRC calculation including other predetermined fields in said packet; transmitting the results of said CRC calculation with said packet.

1 1 . The method defined by Claim 1 0 including the additional steps of: receiving said packet; calculating the CRC for said other predetermined fields of said packet using said system identification number in said calculation; comparing the results of said calculation with said results of said CRC calculation transmitted with said packet.

1 2. The method defined by Claim 1 0 wherein the portion of said CRC calculation using said remaining bits of said N bit identification number is stored for use in subsequent CRC calculations.

1 3. The method defined by Claims 10 or 1 1 including the additional step of converting said predetermed fields of said packet into segments of six bit codes where each segment comprises three binary ones and three binary zeroes.

14. In a network for sensing, communicating and controlling where said network includes at least a first and a second media, an improvement comprising: a first plurality of cells coupled to said first media; a second plurality of cells coupled to said second media; a third cell coupled to both said first and second media; at least one of said first cells and one of said second cells having a common group identification number (common group ID) and being assigned tasks to carry out a group function for said group identified by said common group ID; said third cell having said common group ID for purposes of repeating messages broadcast between said cells having said common group ID; whereby sensing and control over a network having a plurality of media is achieved.

1 5. The improvement defined by Claim 14 wherein said third cell rebroadcasts said group messages onto both said first and second media.

1 6. The improvement defined by Claim 1 5 wherein said packets are encoded with a 3-of-6 codes, each code containing three binary ones and three binary zeroes.

1 7. In a network for sensing, communicating and controlling having a plurality of cells a method for infering a collision has occurred between packets transmitted by said cells comprising the steps of: transmitting a first packet by a first of said cells, said first packet requesting a reply from at least a second cell and a third cell; waiting a predetermined period of time for a reply from said second ceil and said third cell; infering that a collision has occurred if a reply is not received from either said second cell or said third cell.

1 8. In a network for sensing, communicating and controlling having a plurality of cells a method for infering that a collision has not occurred between packets transmitted by said cells comprising the steps of: transmitting a first packet by a first of said cells, said first packet requesting a reply from at least a second cell and a third cell; waiting a predetermined period of time for a reply from said second cell and said third cell; infering that a collision has not occurred if a reply is received from at least one of said second cell or third cell.

1 9. In a network for .sensing and communicating and controlling where a plurality of cells are coupled to said network, said cells communicating with one another with packets containing messages, an improvement comprising the steps of; transmitting by a first cell a sequence number with each of said messages and a retransmission flag indicating whether the message is being retransmitted by said first cell; acknowledging one of said packets by a second cell if said sequence number in said packet is different than the previously received sequence number, and, if said sequence number is the same as said previously received sequence number, acknowledging said first cell only if said retransmission flag in said packet indicates that said packet has been retransmitted by said first cell, whereby unnecessary acknowledgements to packets are prevented.

20. The method defined by Claim 1 9 wherein said second cell takes action on said message only if the sequence number is different than said previously received sequence number.

21 . The improvement defined by Claims 1 9 or 20 wherein said packets are organized into segments of six bits where each segment contains three binary ones and three binary zeroes.

22. In a network for sensing, communicating and controlling where a plurality of cells communicate with one another with packets each of said packets comprising a plurality of first fields, an improvement comprising the steps of: including with said packets a second field the value of which is determined at the time the packet is transmitted; including with said packet a first verification number calculated for said first fields, said first number being used to verify the accuracy of transmission of said first fields; including with said packet a second verification number calculated for said second field said second verification number being used to verify the accuracy of transmission of said second field; whereby said first verification number may be calculated before said second field is determined.

23. The method defined by Claim 21 wherein said first verification number is a cyclic redundancy code.

24. The method defined by Claim 23 wherein said second verification number is a cyclic redundancy code.

25. The method defined by Claims 22 or 23 wherein said second field represents the total time waited by all of said cells to transmit one of said packets.

26. The method defined by Claim 25 wherein said packet as transmitted contains 6 bit segments each having three binary ones and three binary zeroes.

27. In a network for sensing, communicating and controlling where a plurality of cells communicate with one another with packets an improvement method comprising the steps of: each of said cells determining the baud rate of each packet received over said network; storing said baud rate within each of said cells; any of said cells replying to any of said packets with other packets, said replying cell transmitting said other packets at said stored baud rate.

28. The method defined by Claim 27 wherein said stored baud rate is used for contention slot timing.

29. In a network for sensing, communicating and controlling where a plurality of cells communicate with one another through packets, an improvement comprising the steps of: each cell determining the baud rate of a received packet; each cell storing said baud rate within said cell; any of said cells replying to said packet, using said stored baud rate for contention slot timing.

30. The method defined by Claim 29 wherein said stored baud rate is used by said cells as a transmission rate for transmitting a reply packet.

31 . The method defined by Claims 27 or 29 wherein said packets contain segments of 6 bits, where each segment comprises three binary ones and three binary zeroes.

32. In a network having a plurality of cells which communicate with one another with packets where each of said cells includes processing means for preparing and interpreting said packets, some of said cells for repeating said packets (repeater cells) an improvement comprising: a field in said packets representing the time one or more of said repeater cells waits to transmit a packet; said processing means of each of said repeater cells including means for counting the time said cell waits for transmitting a packet and means for operating upon said field to indicate in said field said time said cell waits, whereby an improved network is realized.

33. The improvement defined by Claim 32 wherein when said field reaches a predetermined number said cell discards said packet rather than transmitting it.

34. The method defined by Claim 33 wherein said processing means calculates a cyclic redundancy code for said field.

35. The method defined by Claim 34 wherein said packet contains segments of 6 bit codes, each code having three binary ones and three binary zeroes.